Many fans are confused over which killer (Billy and Stu) was behind the mask during the following murders and attacks. Casey and Steve's murders: Billy and Stu were present because Ghostface is at both entrances. It is implied these two were killed because Casey dumped Stu for Steve, making the killings personal to Stu. It is the Ghostface at the back entrance who made the calls to Casey, because it was the Ghostface at the back of the house because when the caller reveals that he intends on killing her, he tells her to "turn the patio lights on... again", which are at the back of the house and the "again" implies that he is already aware that she has turned on the patio lights before since the first call. The Ghostface that gutted Steve was logically the Ghostface at the back entrance of the house who is Stu as that is where Steve's body has been placed. The Ghostface that is seen running around the house after a chair is thrown through the patio doors was the Ghostface in the back as Ghostface came from the back of the house. After Casey is stabbed and choked, she removes the mask of the Ghostface from the bushes and recognizes the face she sees, hinting at the killer being Stu, which would also imply that the Ghostface at the front entrance was Billy and Stu's grunts can be heard as he recieves blows by Casey. Billy assisted Stu in gutting and hanging Casey from the tree due to how quickly this action was executed. Sidney's house attack: Billy most likely called Sidney while Stu attacked her. Billy is seen with a phone and appears at the bedroom window too soon after Sidney locks herself in her bedroom. For Billy to be Ghostface here he would have to have run downstairs, go outside to run around the perimeter of the house, ditched the Ghostface costume, and climbed into Sidney's second story window in a matter of seconds. This is further proven if one listens carefully as Ghostface chases, receives blows and is tripped by Sidney as he continuously grunts with his voice attributing to that of Stu. Call at the Riley house: Stu called to 'prove' Billy was innocent since he was locked up at the time, but it could've been Billy using his one phone call from jail to call Sidney in the ghostface voice. Sidney's bathroom attack: It would be Billy as the Ghosface had the same colored pants Billy wore. Also, Billy copied the same words the girls said about Sidney and her mother when Billy revealed himself as one of the killers. Billy wanted to hear Sidney's emotions and weaknesses or it could've been a prankster as the assaliant didnt have a knife Principal Himbry's murder: This murder was most likely Billy as his whereabouts were unknown at the time. Stu was seen with Sidney and Tatum outside the school, but left somewhere unknown. Even though Stu left somewhere, Billy had the better chance of killing Mr. Himbry. Stalking Sidney and Tatum: Evidence lays more on Billy. Billy was the one that attacked both of them and possibly wanted to know more about them. Tatum's murder: Billy, later shows up gives Stu a face signal that he killed tatum Billy's fake 'murder' and Sidney's attack: Obviously Stu because Billy is seen. Kenny's murder: since Stu claims that Gale died when she crashed into a tree with the news-van after finding Kenny's dead body. It is most likely that Stu stuck around the area in front of the house, even after Sidney got away. Dewey's attack: Billy, he hears Dewey yell, puts on the costume, goes downstairs, stabs him, chases Sidney, either goes threw a window in the house, or the garage and pretends that nothing happend. Stu was checking to see if Gale was dead and was around that area, not the house. That explains why Randy was blaiming Stu for killing the people becuase he was stalking him since he was already outside when Gale hit him with a phone. Neil Prescott's abduction: Billy and Stu kidnapped him in order for them to frame him, because they both wanted people to believe that Neil Prescott was the killer.