I was being flippant.
If I had time to think about it beforehand (say, if I was dispatched to "possible bomber in a boat"), I'd set a perimeter at standoff distance and bring in the pros, who are trained and equipped at dealing with people who are likely to explode when you shoot them.
If the bad guy popped up in front of me and started shooting, I probably wouldn't have time to think about it. I'd fire, then say to myself, "Holy shit, it's a good thing he didn't blow up!"
Okay, I'll bite.
Here I am, a cop called to a modest home with a boat in the back yard. Lots of other homes around in all directions. I'm part of a perimeter, meaning that my target is somebody that evidently is in that boat, bleeding.
Now all of a sudden, the jagoff that's in the boat rears up and sprays the area with gunfire. I'm behind cover, but due to the neighborhood, there's no way in hell I can be certain of what's downrange beyond the boat. Other officers have begun clearing out the neighborhood, but I can't be certain that for me, the properties beyond the boat are clear.
So now, despite all that, I'm rattled enough to engage the jagoff.
Brilliant. Just brilliant.
Oh, just for kickers, the jagoff is still breathing. We bring in a robot to check.
I dunno. I'd hate to be a Watertown/Mass. State Trooper/Boston cop about now. The LEOs across the nation have all got to be shaking their heads in utter dismay.