Aaron

Aaron was a one-time appearance character played by James Bendishaw. He was the boyfriend of Haley Meyers. In Season 2's premiere I Know What You Did Last Summer, Aaron participated in a prank with Haley against Audrey Jensen. In the prank, Aaron, dressed up as the Lakewood Slasher, would chase Audrey and pretend to murder Haley. However, after "murdering" Haley, Aaron continues to scare Audrey only to be stabbed in the chest by her with a ice pick. Amazed by this, he drops the floor, injured while Haley stops pretending to be dead and explains the situation. According to Sheriff Miguel Acosta, the camera strap around his chest was thick enough to prevent the pick from going further into chest which saved his life. Aaron is never seen again. In the second episode, Psycho, when Audrey received a text from the killer, she finds that Haley was staring at her while texting at the same time. Audrey confronts her and reads her text where we learn a recovering Aaron is texting her probably at the hospital since he's apparently not at school to be with her. 

Apparently Aaron and Haley broke up or she cheated on him with the new killer because in The Orphanage, we learned that Haley set up a party at Piper and Lang's old orphanage as a favor for a "special friend" whom she tells Emma that she's seeing. This "special friend"/new boyfriend turned out to be the killer who then kills Haley.