I've been thinking about this situation since the tragedies of that particular day. I have several responses to the OP's question....
- If my children are with me and my wife is not, I stay hunkered down behind cover and ready to protect them. Period.
- If it's just my wife & I, or my wife & I + the kids, I order her and the kids behind cover and tell her to call 911 and give them my description and make sure they pass to responding officers the fact that I am armed. Then, I cautiously make my way towards the shooting. I stay behind cover if available, but under the circumstances (innocent people being shot), concealment will suffice. My weapon will remain holstered until I can see what's going on. If the shooter is still shooting, I will engage to stop the deadly threat to innocent life. If I cannot readily 100% identify the shooter, I stay behind cover/concealment and mentally record everything for police, weapon still holstered, but ready to draw.
- If I am alone, I call 911, put the phone on speaker (or use the earbud I normally have with me) and put it in my shirt pocket, I'll tell them everything as I make my way to the scene, response at scene will be the same as above.
I'm sure there are those who will disagree with me. I fully expect it and understand their arguments against engaging the threat. The difference between me and the 'average Joe' is that if my actions land me in court, I can fall back on the considerable amount of training and LE experience I have in the CG. My defense would center around the actions a "reasonable and prudent person" would expect from an off-duty federal LEO in such a situation.
It is a tough question to answer, but I view it the same as I would approaching a vehicle accident on a highway; Yeah, it's dangerous, potentially deadly, but I signed up to help people, protect people, and enforce laws. My (personal) obligation to do so does not stop when I step off the ship... I'm reminded of a line from the Coast Guardsman's Creed I memorized in boot camp long ago... "I shall sell life dearly to an enemy of my country, but give it freely to rescue those in peril."