When I was two, I bit my sister-in-law on the arm. Over 20 years later, I was on vacation near where she and my niece were living (long divorced from my brother). I went to pick up my niece to take her to dinner, and when I knocked on the door, my niece just hurried outside. I asked her if her mom was sick or something and didn't want to say hello, and she explained that her mom didn't like me because I had bitten her when I was two years old. 20 more years go by, and I notice that the ex-sister-in-law is facebook friends with all my many siblings except me. She is literally still holding a grudge against a two year old, for over 40 years now. That's extremely immature and rather pathetic of her. And, truth be told, I actually remember biting her (yes, I can remember being two), and from my perspective she deserved it as she was trying to boss me around and she wasn't my mama! LOL, no I don't still think she deserved it, but that was my thought process at the time.
Anyway, she's managed to hold a grudge against me for over 40 years. However, she has yet to shoot me in the back.
I really can't imagine calling someone a "loser" as a teenager is a reasonable motive for cowardly shooting someone in the back over a decade later. Especially one's own flesh and blood, one's only child. And if someone was so irate about it after that much time, one would imagine there would have been physical blow-ups prior to the shooting.
I have wondered, however, how some of the other people involved might react to being called a name. People react to blows to their egos differently, depending on how big said ego is, and if that person manages to have an internal locus of control or not.