Build a movie plot around this: Why does Peter kill Stephen? He had been turned into a Zombie (Dawn of the Dead 1978)
The answer to this question is:
Tensions are running high in the United States. The recently deceased are returning to life as shambling, flesh-eating ghouls, and political dissidents are threatening social stability. In the city of Philadelphia, Fran (Gaylen Ross) an employee of WGON-TV and Radio learns that her program director Givens is broadcasting out-of-date information about rescue stations that have been overrun by the living dead. Fran's boyfriend Stephen (David Emge), who pilots the station's traffic helicopter, arrives at the station and tells her that they must escape in order to survive. He plans on stealing the station's helicopter and tells Fran to meet him on the roof at 9pm.Meanwhile, in another part of Philadelphia, the city's SWAT team is preparing to launch an assault on a low-income tenement building filled with refugees who refuse to leave their homes for emergency shelters; they also refuse to give up their dead, both deceased and re-animated, harboring them in the basement of the tenement. After gun battle with armed bandits on the roof, the police and National Guard soldiers break into the building using tear gas. Roger (Scott H. Reiniger) one of the SWAT troopers, becomes disgusted by the bloodthirsty behavior of some of their fellow SWAT members when one of them goes crazy and begins shooting at both zombies and innocent bystanders. A tall figure in a gas mask shoots the rogue officer dead. Roger retreats to the basement to escape the confusion, but the tall figure follows him. He removes his mask and reveals himself to be an imposing man named Peter (Ken Foree). They have talk for a few minutes and agree that the zombie plague will only get worse. Roger tells Peter about his friend who has a helicopter; he plans to leave with Stephen and Fran, and suggests Peter join their escape. A priest emerges from a room in the cellar; the man is missing a leg and walks with a crutch. He tells them that he has administered the last rites to the dead people in the next room, and that the soldiers may now "do what they will"...