good cops wouldn't?

Commenter Our Family is His makes an astonishing assumption, so astonishing that I wondered if I misread her attempt at humor.

Thankfully good cops wouldn't shoot an innocent person doing nothing, so while you were emotionally hurt so much that day and your husband decided to rip your family apart, you were safe that day.

Good cops would have investigated to see if any of us have a history of violence. 
Good cops would have questioned the need to come into my home with their weapons drawn.
Good cops would have waited until the children were out of the house.

Good cops wouldn't shoot an innocent person doing nothing? 

Sometimes the resulting damage, injuries, and deaths have less to do with whether the cops are good or bad than to do with the dangers inherent in drawing weapons in a chaotic situation. Too much chance for unexpected movements or sounds, too much chance for misunderstandings, too much chance for adrenalin to lead to mistakes.

Good cops understand that and avoid creating that chaos.