I've only known one person who shot and killed another human being outside of being a soldier in a war zone. She was an older (I'm guessing early 70s maybe) security officer at the community college campus across the street from our home in Missouri. Early one morning I saw a hawk who had gotten entangled in the soccer net across the street, so I called the campus cops to see if someone could let me into the fenced area to rescue him. Margaret, the security officer, appeared. We managed to free the terrified bird w/o getting injured ourselves, then got to chatting. She had retired after decades as a St. Louis City police officer, and worked PT for the college. At one time she had had a suspect fire at her, so she fired back and he died. She said that the PD offered counseling. She did that, but said even so it "almost destroyed me." He was a very bad person with many felonies for violence, plus prison time. But still. One human takes another's life, and both are hurt.
People who think that civil wars are cool, shooting protesters is cool, shooting someone who annoys you is cool -- either they got that idea from video games and movies and have no idea. Or they have no souls.