[THEUPMAN]

Pulling a gun is a very serious step , and should not be taken lightly.

If the guy thought that he, or some other person was in danger then, yes , he had every right and even an obligation to secure their safety.
But ..... stealing a generator is not a death penalty offense. Nor is running away with one.

His priority should have been simply to secure the safety of the people on the scene.

There is no room for error once the trigger has been pulled.

But ... after saying this , I believe it's clear that this guy did nothing wrong.
He did not shoot the perp.

Where as the threat of force didn't stop the guy from stealing , it probably did have the effect of enhancing the safety of the people .
In other words ... the bad guy was getting out of town , not going back for seconds, where he could have possibly hurt someone.

If the bad guy had turned to threaten the good guy the good guy would have been justified in pulling the trigger. And in that event it would have been prudent to have his arm at the ready.

Give him a raise and a medal.

[Publius Valerius]

But ..... stealing a generator is not a death penalty offense. Nor is running away with one.

In my state, prevention of a felony justifies use of deadly force. Generators aren't cheap, and query as to whether this qualifies as a felony, but I don't think using deadly force--which he didn't even do here--would be out of line.