Procrastinate Take no action until it is as safe as possible, and necessary. Investigate Remember, this is a crime scene. Do not exceed your authority but support and assist the investigation as appropriate. Decontaminate and clean up carefully to avoid accidental removal of evidence and to avoid endangering others. It is the scene of a deliberately violent and lethal act.
Second priority is preservation of evidence.
Examine victims for injuries and weapons. A perpetrator may have been injured, too. Use personal protective equipment. Stay clear of spills, vapors, fumes, and smoke. Use fog streams instead of solid streams where possible to preserve evidence.