Okay these aren't confirmed facts by the writer Kevin Williamson but these are who I strongly believe were behind the mask.
Casey and Steve - Stu killed them both while Billy called them. Billy was obviously the caller as Stu was not that bright, and the killings were much more personal to Stu. And when Casey takes the mask off before she dies she recgonizes the person, so it's Stu.
Sidney's attack - Stu did it while Billy called again. There's no way Billy could've ran down the stairs, ditch the costume, and climb up Sid's window in a matter of seconds.
Sid's bathroom attack - I personally think this was a prankster cause one, he had no knife, and two, I don't think Billy or Stu would risk it. They had too much on the line.
Himbry's murder - Probably Billy as Stu was busy inviting people to his party. I think that was the plan, for Billy to kill Himbry while Stu invites people cause they had alot planned for that party.
Tatum's murder - Definitely Billy. People would've noticed if Stu, the host of the party, was gone. And Billy gave Stu a look that basically meant 'It's done.'
Kenny's murder - Stu did it while Billy played dead.
Dewey's attack - Stu again. I think he did everything after doing Billy's fake murder. This would explain why he had the knife once he and Billy revealed themselves at the end.
The main thing you have to remember with each kill is that Billy and Stu have their own method of killing each victim. This helps to narrow down who actually killed who.
Steve's murder - Stu
Billy was on the phone with Casey. He was the one obsessed with horror movies and clearly the brains behind the killing spree. Plus, he got off on intimidating people, as we saw in nearly every scene he was in.
Billy signalled for Stu to gut Steve, who did so while the lights were off.
Casey's murder - Billy
Kevin Williamson confirmed that Stu killed Casey on his Twitter, but I do not consider this movie canon. Williamson may have written the script, but Wes Craven clearly had a different intention in mind with his direction.
Firstly, there is a common theme with all of Stu and Billy's attacks. Stu had a habit of stabbing only once, while Billy stabbed multiple times. This was actually hinted at in the final scene, when Stu stabs Billy once ad Billy stabs Stu up to four times. Casey was repeatedly stabbed, which hints that Billy did it.
Secondly, Casey was strangled after the first stabbing. Of the two killers, Billy is the only one who performed this later on in the film, when he strangled Sidney. It's his killing method when he does not have a weapon. The fact that the killer immediately strangled Casey after losing his weapon points the guilt a Billy.
Thirdly, the technique in which Billy and Stu hold the knife is another tell. Stu holds the knife with two hands over his head, while Billy holds it with one hand and his shoulder arched back. Casey was stabbed using the latter technique.
Finally, people point to Casey's reaction as a clear sign that it was Stu underneath the mask. But they're ignoring the fact that Casey would have known Billy well, since he was her ex-boyfriend's best friend. Her facial expression could easily be that of recognising Billy.
The fact that there are three separate clues pointing to Billy makes it pretty clear to me that it was him. Plus, from a director's perspective, you would definitely have your main killer performing the act at the crucial moment, and Billy was obviously the main antagonist of the film.
It was Stu who got hit by the phone through the window, and then Billy threw himself through the second window to chase Casey when Stu was knocked out. After all, Billy and Stu were waiting at the front door and patio doors, so it would only make sense for one killer to chase Casey once the other killer got knocked down,
Sidney's attack at home - Stu
Again, we go back to the holding technique. The killer held the knife over his head with two hands, which hints that it was Stu. You can also hear him say "Easy, easy," as he chases Sidney up the stairs. In the following school scene, we also hear Stu say "Easy," as Tatum hits him.
In addition, Billy appeared in Sidney's window almost immediately after Ghostface had left the room. There is no way he could make it down the stairs, around the house and up to Sidney's window in that time.
Sidney's attack in the bathroom - Another student
The whole school knew about Sidney's mother's murder, and they would also have been made aware of the attack at Sidney's house the previous night.
The key factor is that Ghostface wore black pants and did not have a knife. Billy was in blue jeans and Stu in light brown pants. This was confirmed in the video store scene.
As for how they got in there without being seen and knew that Sidney would be there at that exact time, remember it's a movie, so we have to suspend our disbelief.
Himbry's murder - Billy
Both Billy and Stu's whereabouts during this time was unknown, so it could have potentially been either of them. But I have to go back to the rule of killing technique to solve this one.
Himbry was stabbed repeatedly using one hand to grip the knife. And as we have seen throughout the film, this is Billy's preferred technique.
Tatum's murder - Billy
I was very tempted to go with Stu on this one, particularly how clumsy the killer seemed to be during the scene, but the clues point to Billy.
The obvious hint would be that Billy shows up to the party immediately after Tatum is killed. And the look he gives Stu at the door seems to be a hidden message.
I also have to believe it would be very difficult for Stu to leave his guests without them getting suspicious, particularly if he comes back alone.
As for why super-meticulous Billy was suddenly so clumsy, it was clearly added for dramatic effect to make the audience believe Tatum had a chance to escape. Once again, suspension of disbelief.
Kenny's murder - Stu
Billy was playing dead upstairs and he couldn't risk Sidney potentially heading back into the bedroom and finding Billy's body missing.
In addition, Kenny had his throat sliced open in one motion. Again, that would be a sign of Stu's killing technique.
Steve: Billy was the caller, as he was obviously the more taunting and evil killer of the two. Definitely not one to be messed with. Stu stabbed Steve to death in the chair. Both were there.
Casey: Again, Stu was the killer, and Billy was the caller. Nothing changed, and Stu killed both of them. It all fits that they were the first to be killed, seeing that Casey dumped Stu for Steve. That look when Casey removes the Ghostface mask. Also, in regards to whether Stu was with Tatum the night before, probably he was, some of the time. Teenagers are quite naïve anyway.
Sidney's Attack: Billy was the caller, and Stu was the attacker. Billy was calling from outside somewhere, watching Sid walk across the front porch, and eventually gave Stu the chance to run inside and hide in the closet as Ghostface. Billy wanted to be framed for the attack and proven innocent as he had an accomplice so no one would suspect him.
Sidney's Bathroom Attack: Billy, and I really don't know how, but I believe so. It could not have been a prankster, something to me just doesn't fit right with the way the killer was acting.
Himbrey: Billy. Stu was outside inviting party guests, and Billy, having already attacked Sidney in the bathroom - you just get that feeling that he never left the school that afternoon. He wanted the headmaster out of the way so that he and Stu's plan to kill Sidney would work at Stu's by providing a 'telephone' call to Randy to lure the party guests over to the football field of the school. That left only Sidney, Dewey, Gail, Stu, Randy and Billy at the house.
Killer In the Bushes & Grocery Store: Not a prank, definitely. It was Billy, watching and observing to see what would happen, and how the party would be set up, seeing as Billy was banned by Tatum from attending. Also, the grocery store scene - she was overheard by Billy insulting him.
Tatum: It was Billy. Stu had knowingly set her to her death to get her out of the way and Billy into the party. As for how the killer did this entire scene the entire time, I don't know. I believe Billy was hiding in the garage the entire time, and maybe Stu closed the door and locked it shut? Stu had no time to leave for that long unnoticed. Billy kills her, then proceeds into the house and likely out of the back door to re-enter through the front door. There, he gives Stu the nod.
Who Reported Neil Prescott's Car In The Woods?: It was Stu. During the movie scene where him and the other teens are watching a horror film, he leaves and grabs another beer. That gave him enough time to use his own voice (or the voice changer) and call the cops to report Neil's car to get rid of Dewey and Gail. Who called Randy to advise that the principal was hanging dead on the rugby post? Don't know. Could have been Stu using the voice changer, or someone else. It all happened at the right time though, as most of the party goers fled.
Behind Randy & Kenny: It was Stu in both cases. Even though Skeet Ulrich was the one in the costume, what all went down points to Stu. The killer was quite clumsy, leaving Randy without killing him just to run after Sidney's calls for help, slashing Kenny and then oddly crawling out of the back of the van (something Stu would do). After she escaped, Stu must have hid somewhere, then went after Gail when she crashed the news van as it was confirmed near the end.
Dewey Stabbed: Definitely Billy. Again, this is another intuition, but at this time Stu was still attending to see whether Gail was dead or not, or on his way back. The killer treated Sidney as if it were Billy, toying around with her, running away. There is no way Stu could have escaped, taken off the costume and not been caught by Randy. Literally five seconds later, Stu and Randy come running to Sid out of nowhere.
The Casey/Steve killer is questionable. I think Billy killed Casey and Steve. Stu had an alibi. When they are all (Sid, Tatum, Billy, Stu and Randy) sitting around the fountain towards the beginning of the movie, they are talking about being interviewed by the cops and guessing who may have been the killer. When it's brought up that Stu used to date Casey, Randy specifically asks him "where were you last night?" And Tatum says that Stu was with her. I guess it's theoretically possible that Stu snuck out while she was asleep or something but that seems far fetched. The houses are clearly not close together as shown in the beginning when Casey's parents are driving home, when Sid is running from ghostface at Stu's later etc. Stu was interviewed by the cops and the alibi checked out. The timeline doesn't add up. Billy had no alibi and was out and about that night when he went to Sids- "did you happen to swing by Casey Becker's house that night too?" Finally, people always look to the boyfriend or the ex so while Stu was in on it, having Billy actually carry it out would be less obvious and a clever diversion.
You're right.....Billy Killed both (Casey and Steve), Stu was with tatum in the night of the murders, Tatum said that Stu and her spent all night together, so is impossible be Stuart....Tatum will not lie about it, she was inoccent, no reason to lie and protect Stu.....But Billy was the one who went away in the night...and after killed Casey and Steve he went to Sid's house.......after, when Billy was arrested, in the Police Station, Billy, his father and the chief were talking, and Billy's father didn't know that Billy was not at home last night.....it sure was him !!!
I saw this movie around 1997.. i was only about 19 and it is a time capsule of a lost youth lol.. We went over lots of this stuff back then but i had to dig it out once more after seeing the film on the tv guide station last week. Heres what i have come up with over time as well as recently.. who killed who?" Casey and Steve: Both Billy and Stu were present. Stu was in costume and did all the physical killing of both.. while Billy was the voice on the phone asking trivia about horror movies in exchange for chances to survive. Billy was primarily the one obsessed with horror movies even seen standing in the horror section of the video store. Billy acted as "the brains" and gave the orders to accomplice Stu.. to place Steve on the patio (as well as cut his guts out for when the lights came on). There remains very small chance that Billy killed Casey and maybe even Steve as well ONLY because of the methods of strangling and stabbing multiple times. However simply by knowing Stu dated the victim then it is obvious just by the look on Caseys face when the mask is pulled off that someone she recognized was the killer (this was confirmed recently Kevin Williamson twitter and he wouldnt joke around) Had Casey seen Billys face ... this part wouldnt make any sense at all. So thanks KW for the confirm after all this time! Stu did have a sort of "alibi" from Tatum that is very easily explained away.. Billy and Stu both planned to go from the murder scene to their respective girlfriends houses later.. just like billy was at Sidneys house as well. I think the early changes in the typical Stu killing style probably came from Wes Craven (rip).. perhaps i read because the director felt that in order for the movie to be effective as it was.. that opening scene had to be gory and drawn out (or Stu was just extra eager to take revenge against someone).. either way Stu took the opportunity to murder Casey and Steve as reward for his part in helping kill Sidney. The two victims had been promised to him by Billy Loomis who had played on Stu's pain and weakness.. just as Roman had done to Billy prior by coaxing him into murdering Maureen by telling him SHE was the reason his family split apart ruining his life) First attack Sidney: Stu was in the costume again with Billy making the calls. The formula did not stray very much from the prior murders. Billy distracted Sidney on the phone drawing her outside to the porch.. this gave Stu a chance to hide in the house. The line about Sidney's mother also a dead give away. Billy had been prodded into killing Maureen at Romans request after she rejected Roman as her child.. Billy entered the window and by no accident dropped the phone. He was quickly arrested as the prime suspect. However as it was planned. When Stu called as Ghostface while Billy Loomis was behind bars Billy was cleared as suspect (you must remember the plan the whole time was to frame another man for the killing of Sidney and Maureen this time using her own dad) Stu was now the voice on the phone and things heated up as Billy Loomis took on the disguise to switch the roles. Bathroom Attack on Sidney: I think it was Billy in the bathroom. A distraction occurred as apparently non connected boys pulled a Ghostface costume prank in the hall (were they coaxed? i find no direct proof although are the boys not party guests later? i think so. also i picked out the symbolism and perhaps foreshadowing with the two boys in the principals office on a repeat view). The first theory about bathroom Ghostface suggests that attack on Sidney was just another random prank (if you listen to Ghostfaces voice when he falls he sounds a little diff suggesting it might have been just pranksters). However I dont buy that one. Going with the 2nd theory it was Billy. I got the impression from bathroom stall scene.. where the black robe slid down into sight near a pair of tough looking boots.. the scene is deliberately serious. Perhaps the scene was meant to be a initiation of sorts.. the very moment Billy Loomis, the main antagonist himself, stepped into the Ghostface costume for the first time in the film turned up the seriousness a notch along with the pace. However there was one small point explaining why the Ghostface in the bathroom stall had such obvious wardrobe differences from Billy and Stu. Black jeans and boots and also carrying no knife. This 3rd "sort of out of left field" theory holds that the bathroom Ghostface was neither a prank or Billy.. the "third killer" premise of Scream 1 states the bathroom Ghostface is in fact... Roman from Scream 2. The third killer premise is often sited again in later scenes where Ghostface is seen in background shots.. something neither Billy or Stu would dare try at this point as Billy was already suspect.. but ill get to that. Principal Himbrey: I say Billy. Stu is busy during this scene outside inviting people to his "party" while we get the impression Billy never left the school. With all the chaos going on theres time for Billy who has now gotten into his role full costume.. to take his first victim in the film(not counting Maureen) a warm up for laters perhaps. Himbreys dead body was used by the killers left hanging from a goal post in order to create a distraction phone call to Randy.. knowing that announcement would lure party guests away from the house just long enough to get Sidney alone. Ghostface in Store and bushes: I still say Billy. I loved these subtle touches after a few repeat views. Originally scoffed in disbelief later I felt these little scenes separate Scream 1 from more mundane stalker films. My theory.. I think after the murder of Himbry.. Billy Loomis is taking on the costumed killers persona even more fully.. braver than Stu had ever been using the Ghostface costume (along with the town reeling in chaos) to blend and meld with his own special brand of angst insanity.. that had brewed long in silence (and steeped over one blood soaked horror movie after another.) Michael Myers, Jason, Freddy.. he's got them all beat now. Thats really good. However, i think i still like to think it was the "third killer" Roman from Scream 2 personally.. and since someone mentioned Roman's theory a last time.. Ill add one "4th killer theory of Scream 1" we thought up back then.. a chance for an actual supernatural twist (ghostface is really a ghost).. something the movie teases with it seems but never falls into (thankfully). Tatums Death: Billy. After the last few events leading up I think Stu knew Billy was hiding in the garage in the shadows dressed as Ghostface and locked Tatum out of the house. This way by killing Tatum off it further isolates Sidney for the grand finale. Stu also probably couldnt have gotten out of his casual party clothes to be in and out of costume fast enough..but someone had to shut the door from inside the house. Billy gives Stu a sort of facial expression raising his eyebrows at Stu who is at the door still in a smoking jacket with guests around him as if to say "taken care of". Randy's phonecall: i think Stu had the voice change and a phone to call Randy and use the principals body to get people outta the house. He had just said he was going for another beer and would "be right back" which for me seeing it first time created a minor suspense (would he really die for saying that?).. in which the phone ring breaks and the party goers as planned file out the door for the bigger action. I couldnt imagine that being timed as "an accident" though it is never really explained. Also a call comes to Dewey that Neil Prescotts car was just found in the woods.. an obvious attempt to get more people away from the party. Both calls were probably Stu on the phone as Ghostface while Billy was upstairs getting sexual with Sidney.. a horror movie sin self referenced by Randy meta minutes before.. Stabbed Billy Loomis: well thats obvious. Who Killed Kenny?: Stu yet again.. he stood over Randy in whats become known as the "Stu Strike" pose.. two hands overhead straight down one hit at a time. Lol the fact he is so obviously clumsy had me thinking he HAD to have killed Tatum but again it might have been the director changing things to make the action better for the audience.Stu Ghostface remains until he appears in street clothes again (somehow unbruised welted or with a DROP OF BLOOD ANYWHERE ON HIM..)qith Randy holding his leg that was somehow cut open at the door (who stu left ALIVE by himself there and disappeared to look for Gale.. leave her out the somewhere ALIVE and return in the house to tell the whole plot to Sidney only to be rescued by Gale who now has a handgun aimed at them. Meanwhile Billy rolling downstairs in fake blood (he later said was 'corn syrup') this brings my kill tally: Stu: Casey, Steve, Kenny Billy: Principal Himbry, Tatumbut no need to take my word for it (though i think it makes the most sense) heres a link http://scream.wikia.com/wiki/Body_Count_(Movies)
I think Billy killed casey and Steve, the convo in the beginning when stu says "nah, I didn't kill anybody" and Billy pointedly says "nobody said YOU did" I think it was a clue that he actually never had, since Billy killed Sidney's mom, and the other two murders were cast and Steve and stu was with Tatum, so at this point stu hadn't ever killed anyone yet, I think that's why Billy said it that way.
Billy said "nobody said you did" to remove suspicion, not because Stu didnt killed them. He did. He had the motive. Yes, he usually stab once, but with Casey it was different. Sometime, when a killer have something serious againts someone, he/she might to stray off their usual M.O. Examples:
1. Jill - She usually stab once or twice, but with Trevor (who cheated on her), Charlie (she wanted to frame him as the new generation of Stu, so she stabbed him like a real survivor would've stab his/her attacker) and Sidney (she wanted to kill her cousin in the most cruel way possible) it was different.
2. Mickey - He wanted Cici to suffer, so he asked the more brutal Mrs Loomis to kill her for him. He didnt felt that way, or anything actually (with the possible exception of Derek), toward any of his 5 direct victims.
3. As a non-scream example we have Gaston (beauty and the beast) - He usually either shoot his victims or send his gang after them, but with the beast it was personal, so he wanted to stab his rival (he did stabbed the beast in the back), decapitate him and possibly even disembowel him.
Casey and Steve were both killed by Stu while Billy was on the phone. As people have stated Billy was the one who was obsessed with the horror movies so it'd make sense that he'd be quizzing the victims on horror while Stu kills them. Especially in this case since Stu had a clear motive; Casey leaving him for Steve. This also goes for the attack at Sidney's house. Stu attacked while Billy called.
Bathroom scene was probably either another prankster or Stu as he was always the more clumsy one falling down and everything (as someone previously stated). The theory of it being Roman though is very interesting and could possibly be the case. The black boots and black jeans throw me off as neither of them were wearing this if I'm remembering correctly. This is the only scene I'm iffy on. Not too sure. Could very well be any of the three. I really don't think it was Billy though.
Principal Himbray I'd say was killed by Billy as you don't see him while Stu is outside planning his party with everyone.
Tatum was definitely killed by Billy. The nod Billy gives Stu when he shows up at the door is a clear giveaway.
Kenny was definitely killed by Stu as Billy was still upstairs after being stabbed.
While Randy is on the couch watching Halloween it was Stu as well because Billy was busy playing dead. Which also means the attack on Dewey and Sidney when she's in the car was Stu as well. After that Billy finally comes down the stairs and shoots Randy.