The Threshold For Disarming People Needs To Be Lower

[T]he gunman had no known criminal history, but he was well known to law enforcement.

From the Denver Post.

Five deputies were shot (one died) and two civilian neighbors were shot, before the gunman who was the source of the domestic violence call was killed.

When police respond to a domestic violence call and the gunman was "well known to law enforcement", that person should have been disarmed already and the criminal justice system is failing us.