Trying to take the American perspective:

I suspect that man would have eventually ended up dead anyway to someone legitimately fearing for their life.

There's probably also some calculus of "is society better off without this person?" running through the shooter's head.

Acting as judge, jury and executioner while eating in a diner.

Yes, the "he had it coming" "play stupid games, win stupid prizes" argument.

America has this weird contradiction of being a place where anyone can get rich, be great, etc. But on the other hand, a criminal is irredeemable, can't change, will never get better, will get theirs tomorrow if not today.

That's a very shallow reading of that particular situation. The robber was pointing a gun at people. At the point when someone threatens life like that, regardless of whether the motives are personal or material, it is reasonable and legally justified for someone to use deadly force to end that threat. The only real criticism that can be leveled against that particular shooter is that in hindsight he continued shooting after the robber was arguably no longer a threat.

Or look at it another way. What if the guy being robbed missed, then robber shoots him and all around him. Which would not have happened if the wallets were just given. It's always better to de-escalate.

> That's a very shallow reading of that particular situation.

Yes, with a bit more depth to the reading, you'd know that the robber had already collected the money and was leaving when he was shot in the back.

And what happens when another do-gooder walks into this taqueria, sees this guy shoot someone, and then grab money off the body? Wouldn't that person be in the clear to shoot the first guy?

What if the 2nd guy is a police officer?

It's not clear that the robber was leaving at the time he was shot. The robber was still threatening people with the gun when he was shot. Shooting the robber in the back was a way to get the jump on him—drawing on someone who has already drawn on you is generally suicide.

As for the risk that someone else might mistake the shooter for the robber, anyone who has taken a concealed carry class has learned that there are risks to defending yourself. It's a choice you make because you don't think there are better ones.

But fundamentally, I'm objecting to your characterization that this guy was looking to legally kill someone or that it was motivated out of a desire to keep his wallet. The robber was threatening people's lives. The danger was not over. Shooting the robber was a reasonable choice given what the shooter knew at the time.