Sleepaway Camp II: Unhappy Campers (1988)

Angela Baker escapes from a mental hospital and surfaces at a summer camp as a counselor who lectures her teenage charges on proper moral behavior. Those teens who break her strict rules -- from the camp chatterbox or a sex-obsessed girl to the boys who are peeping Toms -- are murdered by the impostor in various gruesome ways. As more campers go missing, intrepid counselor Molly begins to piece together the truth.