Prom Night (2008) on Netflix

Plot summary

Donna Keppel comes home one evening in Bridgeport, Oregon, and finds that someone has murdered her father and her younger brother. She sees her mother attacked too, and then the assailant turns on her as she goes for help. The attacker is her former biology teacher, Richard Fenton, who had become obsessed with her and had been fired and served with a restraining order. Three years afterward Donna lives with her uncle Jack and her aunt Karen, still in therapy for what she saw. On the night of her senior prom she goes to a hotel with her boyfriend Bobby and two other couples. Detective Winn finds out that Fenton has broken out of a mental hospital and takes his partner Nash to the hotel.