This stuff reaches the level of just plain silliness.
If you're a tax payer you're paying money for services, and one of those services is the animal control officer.
Why make things more complicated (and potentially bad for you) when you don't have too?
CALL THE ANIMAL CONTROL PEOPLE. Let them do the job you're paying them to do.
They'll come out and set up a live trap, baited with tuna.
Cats being cats, the gangster won't be able to resist, and he'll get trapped.
The animal control officer will come out and pick him up.
If he belongs to someone and they claim him, it'll cost them money.
If No one claims him, that's not your problem.
In either event, you won't be seeing him again.
One thing the "shoot first" people never take into account are the unintended consequences for YOU.
Such as:
Someone sees you shooting or otherwise harming the cat and calls the humane society or police.
These days the laws about animal abuse are enforced.
This ain't the 1940's.
These days people get ARRESTED for hurting animals even on their own property.
They also get sued for hurting an innocent Fluffy.
Without some kind of paper trail, it's just your word that the cat was a nuisance.
Second case: You get into some kind of altercation. Maybe a shooting, or just a dispute of some sort.
Suddenly, to the police, prosecutor, or someone's lawyer, YOU'RE the guy who's the hot head who uses violence as a FIRST option.
After all, you're the guy that hurt a poor cat without even bothering to call the proper authorities.
This is one of those cases where you're much better off to "do the right thing" and the right thing is to call the animal control people and let them do their job.
Forget the guns, water, paint balls, and all that. Call it in, and go about your business.