Kill or Be Killed (1970)

Sinopsis

School’s out, and recent grad Dani and her friends are ready for one last summer blowout. But when a senior’s mutilated body is discovered on the high school football field – killed in a disturbingly theatrical fashion – it’s clear that someone is playing by a new set of rules. A red envelope pinned to the corpse contains a yearbook photo and a chilling directive: “Kill or Be Killed”. As the bodies pile up, Dani and her friends are thrust into a terrifying game, orchestrated by a sick killer, that transcends their small town and soon goes viral.