This didn't happen to me, but happened to a close family friend of mine. I hope this doesn't get buried!
My dad used to manage a number of strip clubs and night clubs in the GTA. These weren't the nicest places, and a lot of them were infamous for gang activity, drugs, prostitution, just general greasy shit. My dad has told me a lot of stories about how he was almost killed trying to do his job, which was basically glorified accounting and employee management. Our Family Friend, who's been very close with my father and grand parents since before I was born, worked for him as a bouncer at one of these clubs. The Family Friend was (and still is) a professional fighter, and stands at 6'8, 280lbs. The guy is seriously a mountain of a man.
The owner didn't give a fuck about anything that went on inside, and was content to profit off of some truly dark things happening in his clubs because he would make more money. Still, after a number of shootings, fights and ODs, my father forced him to make a token gesture of cleaning the places up, so a policy of no gang colours was introduced. This really didn't go over well with the seedier clientele.
About a month after the policy change, a guy came in in full gang regalia, openly selling coke, harassing female patrons, and just generally causing problems and being an ass. My Family Friend went up to him and told him it was time to leave. The guy argues with him (Bar ProTip: If you're asked to leave, just go quietly. If you argue, the best case scenario is you embarrass yourself, worst case is you'll be banned). Family Friend grabs him buy the arm, and the gang member pushed him away, and reached to the small of his back to pull a weapon. Family Friend reacted by hitting him with a front kick to his chest. The guy collapsed and began choking. Both my dad and my Family Friend tried to help him, but he died before the paramedics arrived. Apparently his lungs had been punctured by his broken ribs and he died by essentially drowning in his own blood.
My Family Friend ended up serving 11 months in prison for the incident. I'm not 100% sure what happened, but I think he plead down to assault from manslaughter (or whatever the Canadian equivalent of those charges is called) which he says he regrets because he feels he could have won his case on self defense grounds. He doesn't like to talk about the incident, and we very rarely bring it up with him, but he feels awful about the whole thing. He says he wished anything could have been different, that the series of events would have played out without any one getting hurt. He feels responsible, even though by all rights he shouldn't. The guy got himself killed.
It also really affected his fighting career. Loosing nearly a year of training, fights and promotion, plus his reputation as a 'killer', made fights hard to come by for him.