who is the killer in black christmas

In the 2006 remake of the classic slasher film "Black Christmas," the killer is a psychopathic and abusive man named Billy Lenz. Lenz is a former patient of a mental hospital who escaped and has been murdering women in a college sorority house during the Christmas season. Lenz is a relentless and sadistic killer who takes pleasure in torturing his victims, making him a dangerous and twisted individual. The film's ending reveals that Lenz has been hiding in the attic of the sorority house all along, watching the girls through secret peepholes and waiting for the perfect moment to strike.