Not my story, but a close family friend's.

So my family knew this guy who, at the time, was about 70-75. He was a jewish diamond merchant who had fled Europe as hitler came to power on his own in jewels sewn into the seams of his clothes. He then went as far west as he could and started up a business with the stones. Anyway, that was decades before but the point is he was a conflict adverse guy. He was not stupid however, and kept a handgun under his counter for years and years without ever shooting it. Well one night (as I said, at this point he is about 70-75) a group of addicts looking to steal his diamonds comes in as he is closing up. No problem, he says. Take what is out, I have insurance. But they wanted what was in the safe and he wouldn't give it to them, because one of those stones was the last one he had from home before he left for the states.

They beat him badly enough that he nearly died from internal bleeding. His back was broken in 3 places, his skull cracked, I can go on. Basically at this point he was dying. Well as they were leaving the store he reached under the counter (he was on the ground, on his side) and shot all three of them multiple times and proceeded to fall unconscious.

He woke up in the hospital two days later. All three had died, and this old man ended up with pins and plates all over his body. Basically right as he finally finished rehab (about 3-4 years later) he died (heart attack). I am fairly certain that he should not have gotten off with self defense, but these kids had no one to lobby for them and he thought he was dying and killing them would save their future victims. He was probably right.