Forgive the 'soapbox', but like TJ:
...having been shot and having shot at, my perspective is a little different. In my case (the short version)I was in the Rodney king riots in L.A. as a deputy, and two guys charged me while a third distracted me. I was undercover so didn't look armed, but as soon as one guy bounced his fist off my left cheek I whipped a 9mm up to his temple... eye to eye. I could tell he was surprised by the loud, "oh f*ck" comment... then I fired 'right beside his face' whereupon he and all his buddies vanished into thin air.
I reported the shooting, as required, and was promptly written up for discharging my weapon in public because it was considered a "justifiable kill" which I refused to make. Then I quit, and am much happier 'helping people' in SAR vs working under the option of having to decide who lives and who dies.