No, to me it looks like they challenged him. He wasn’t a neighbor...neither of them lived there. Then he got scared because of the shotgun and tried to get it away from them. Also, they had a history and he had had run-ins with the older man (the father).
In any case, it was an accident that he got shot, but they shouldn’t have been doing this armed patrol on their own initiative anyway.
Where did they live?
I see. He was scared so he ran towards and attacked the neighbor with the shotgun. That's a really strange way for a scared person to behave.
No. Someone scared of a shotgun (all normal people) will not "try to get it away from them." They will either run away, or do whatever the guy with the shotgun tells them to do.
Only an insane fool will try to take on a man with a shotgun.