Serial killers break the glass doors into a secure building in order to reach the residents inside. Most residents call each other warning them not to leave their apartment and to lock their doors and use heavy furniture to block the entry to their apartment. As some tenants did not receive the warning, they were killed first, in gruesome ways, then the bodies were nailed up in the lobby of the building. Then the killers worked on breaking in to other apartments. The method of killing became more and more gruesome as it became harder and harder for the killers to get into the apartments.