Who wouldn’t be scared with someone following you with a shot gun? But he should have called police not try and wrestle the shot gun from them.
The father and son should have called the police and not taken things into their own hands. Film him and hand over to police the film.
I don’t think he had much time to do more than react to the gun pointing at him... my gut tells me the two going after him weren’t exactly set on giving him a chance to explain either.