That could work. Movie starts off with the stories of 7 people going about their business staggered a little but each one getting a couple of minutes. Daily lives kinda stuff. Nothing out of the ordinary. But in the background tv/newspapers/general talking about a serial killer on the loose. Have some of them run into each other. But 20 minutes into the movie their stories start their murder so quick 20 second clips of being kidnapped or knocked out from their perspective so never focusing on the killer. Just make it about the victim. Everyone dies. 2 endings - 1 the movie seems to start over with a new batch of people. 2 you see the final killing but never the killer and just the see their shoes walking away as the you are watching through the victims eyes as they close shut.