Hi,
Don't get lazy and put in a raise of 5bb instead of mashing the pot button 
BU's representing a set obviously, unless he's bad enough to also have a better overpair here. The board is dry tho, the only draw is 76 which is difficult for both Hero and the fish to have, i don't really get why he would do that with a set. He shoved his whole stack in with the fish left to act, a fish who donked pot on the flop, a bet which Hero raised. If he just calls there he possibly stacks 2 people, but a good player would recognize the strength of his coldcall and put him on a set immediately. Maybe he feels like he can make his hand look more bluffy to you by just shoving, but missing off on the opportunity to trap the fish in is questionable.
I assume BU is the same guy from the previous QQ hand, which means we're beginning to have doubts on his spazzy shoves ♦ Weird for a guy with such a low AF tho, he can't possibly be doing that all the time. I don't know which hand came first, i think it's this one given the number of hands on BU, maybe you didn't know that yet.
I personally would start to look that guy up once i have a slightly better hand, here something like QQ so that i beat 99-JJ that possibly don't 3bet preflop. As played tho i would fold again for 100bb more, at small stakes i prefer to see people do stupid stuff once before i start to assume that a shove into 2 people, one of whom is a fish, doesn't equal pure strength on a dry board.
Hope it helps.
