Sleepaway Camp (1983) on Netflix

After a horrible boating accident kills her family, Angela, a shy and sullen young girl, moves in with her eccentric aunt Martha, alongside her protective cousin Ricky. One summer, Martha sends the kids to Camp Arawak. Soon after their arrival, a series of bizarre and increasingly violent accidents begins to claim the lives of various campers. Who is the twisted individual behind these murders? The disclosure of the murderer's identity is one of the most shocking climaxes in the history of American cinema.