The Trigger Effect

The Trigger Effect is a 1996 thriller film written and directed by David Koepp, and starring Kyle MacLachlan, Elisabeth Shue and Dermot Mulroney. The film follows the downward spiral of society during a widespread and lengthy power outage in Southern California.

Social unrest ensues due to the persistent blackout, leading Matthew and his best friend, Joe, to buy a gun. When an intruder breaks into the couples house during the night, the two friends manage to chase him outside, where a neighbor shoots the intruder. The neighbors conspire to cover up the fact that the deceased intruder was not armed.As the blackout continues for days, over a massive but undefined area, more chaos occurs. The group decides to flee to Annies parents house, 530 miles 850km away. They do not have enough fuel to travel the whole way, so they stop by an abandoned car hoping to siphon some. A man is lying in the backseat. Joe notices that the man has a handgun, so he heads back to their vehicle to get his own shotgun. Joe aims the shotgun at the man to scare him off, but the man shoots Joe and steals their vehicle. ........

Source: Wikipedia