LEO Training for Active Shooter
Not sure if this was mentioned but there is a nationwide push by all LEO's to have a standardized training for "active shooter" response. I'm a trainer for the US Border Patrol. This enables officers and agents from different agencies that happen to be both on scene and armed at an active shooter situation to be able to form up as an impromptu tactical team and agressively go after the subject or subjects. We are no longer trained to wait on SWAT. I can't go into specifics because of the sensitive nature of the training but it covers and standardizes basic CQB formations, etc... for officers so they can basically show up on scene and automatically function as a tactical team and clear rooms, use bounding cover, etc...
I advise armed civilians, who I support fully, to use caution around these situations and to avoid involvement if possible so as not to get confused for a threat and shot. We get paid to do this. Obviously if your life is in imminent danger or its expedient to use deadly force to stop a rampage shoot away, but please don't go room clearing because it's an already confusing enough situation for us without armed friendlies running around that may be accidentaly shot.