Billy Loomis

"You're as crazy as your son was!"

- Sidney to Debbie Loomis about his son Billy. "What did you just say? Was that a negative, disparaging remark about my son? About my Billy?"

- Debbie Loomis to Sidney about her son Billy.

"we all gonna mad sometimes ...Anthony Perkins "Psycho"!"

- Billy revealed as the killer after he shot Randy

Billy Loomis was the main antagonist of Scream and was a horror film fanatic who pressured his best friend, Stu Macher, into commiting a killing spree in Woodsboro out of anger for his parents' separation.

He was portrayed by Skeet Ulrich.

Background
Roman Bridger showed Billy video footage of Hank Loomis having an affair with Maureen Prescott, his girlfriend's mother. Roman convinced Billy to murder Maureen because she was the reason Mrs. Loomis left Hank and Billy. Roman told Billy to get an easily controllable accomplice he could pin on the murder if it went wrong (Stu), and to frame another of Maureen's lovers (Cotton Weary). Billy and Stu followed the plan perfectly.

Scream
A year after Maureen's murder, Billy and Stu killed Casey Becker and Steven Orth. His choice of apparel is a generic Halloween costume that several people own, making finding the killer almost impossible. This killer is now known as Ghostface. They then begin to target Sidney. He is arrested after finding a cell phone on him the night Ghostface strikes her house. He is released due to lack of evidence as well as the fact that the killer continued to call Sidney, even while Billy was incarcerated (it was actually Stu calling).

In the climax of the film, it is revealed that Billy and Stu took turns doing the killings while the other did the calls. They devise a plan to kill Sidney and frame Sidney's father for the killings, but after being distracted by Gale Weathers, Sidney is able to escape and ultimately kills Stu. Billy suddenly attacks Sidney, and just as he is about to stab her, Gale arrives and shoots him. As they gather around his "corpse", he jumps up, only to be shot in the head by Sidney, killing him for good.

Scream 2
Mrs. Loomis attempted to avenge his death with another killing spree. She killed Randy because he bad-mouthed Billy while on the phone with her, and was eventually shot by Cotton Weary to save Sidney's life.

Scream 3
Sidney remembered conversations with Billy when she visited her bedroom set in the Stab 3 studios. She smiled at his sweet side before she thought of his sinister side.

Trivia

 * He was described as "a young, strapping boy of seventeen. A star quarterback/class president type of guy. He sports a smile that could last for days" in the script.
 * Named after the heroic Dr. Sam Loomis from Halloween, who was in already named after one of the protagonists, Sam Loomis, from Psycho.
 * Billy quotes killer Norman Bates ("We all go a little mad sometimes") and his motive (avenging his mother) is that of Jason Voorhees' first kill. Interestingly, his mothers motive in the second movie was to avenge his death, much like Pamela Voorhees.