I don't know what I'd do in a similar situation. I'll trust his judgement, he was there. I might very well do the same thing.
Did he sleep well that night? Probably better than if he had called the police, they came racing with sirens, the man ran before they got there, and so he would have sat all night wondering.
I think there's a saying in the south "Some people just need killing". It's a good saying, and I believe it fit the situation. That's my take.
Ya hear the joke about a Mexican who walks in on a old Texan playing Doom?