Before the Columbine, Colorado tragedy, the protocol for a lone police officer responding to an incident involving a suspected use of firearms or other weaponry within a building was to wait to engage any suspect(s) until backup arrived. However, the mass shooting in Columbine changed the protocol to demand immediate action. Today, when officers are the first to the scene, they are expected to engage with the suspect(s) immediately, regardless of the risk. This protocol (known as Advanced Law Enforcement Rapid Response Training or ALERRT) has prevented civilian deaths and stopped many active shooter incidents from becoming worse than they did.