One second to decide...
and if you decide wrong, you'll be mentioned in one of Don's posts listing another American casualty.
Sometimes, when someone is under extreme pressure (getting shot at qualifies), he has to make a snap judgement. Click on the link - you have 1 second to decide if the thing being pointed at you is a camera or a weapon. You can then have months of second-guessing from the peanut gallery about your decision - unless you're dead.
Sad to say, but tragedies like this happen in just about every conflict just as they happen on the streets with cops.