Trigger Pull

One of the first questions a lot of people ask cops is "Have you ever shot anybody?". I haven't, but this is how close I came one night:
We responded to a male barricaded in his apartment with a gun. We'd dealt with him before. He would typically call dispatch and just say he had a gun and wasn't coming out, and rather than just leave him alone to do whatever he was going to do, we of course would respond. We'd have to talk to him through his apartment door for a while, then he'd come out and get arrested or go on psych hold or whatever.
This night I was approaching his ground floor apartment, walking up a grassy slope toward his patio. I could see him through the sliding glass patio door, just inside, seated on a couch. The couch was against a wall to the left of the patio door, so he was in profile to me, facing to my right. Obviously, because of the situation and the distance - about 25 feet and closing - I had my gun drawn and at the low-ready.
As I walked up, he stood, put his left hand in his pants pocket, and pulled out a small pistol. As he did so, I raised my weapon, put the front sight center mass, and applied pressure to the trigger with my right index finger. The feeling of my finger pressing that trigger is still as fresh as the moment I did it.
The trigger on a Glock Model 22 .40 cal S&W requires just 5 lbs of pressure and a travel of less than a half-inch to fire a round. I don't know how much pressure I applied to that trigger. Obviously, less than 5 lbs, but not by much. As the guy turned toward me, he tossed the pistol onto the floor and put his hands in the air. I released pressure on the trigger, and my partners and I swarmed him and took him into custody.
I didn't even have to think about it. Years of training kicked in, and I was on autopilot. Only afterwards did I blow my stack. For some reason, it just made me mad. Really, really mad.