Banzai his ass.
There's five of us.
1) He has to a)Hit me and nobody else with the bullet to prevent the attack b)The bullet has to kill/disable if it does hit c)I have a slight chance of beating him physically if I've got mates helping me and not tending to the other guy that got hit (if he missed me and hit a friend) or calling for help. Calling for help in itself would send him running, or should. He's already out numbered. And hell, maybe just maybe Thor will grant me the strength to beat him one on one, I'm skinny not unhealthy.
2)Five of us, one of him. Provided my friends are in normal health and have enough morale they'll join me and we can take turns stomping on the guys nuts before we steal the gun and throw it away. Or since he's threatening us, we can end his life with that bullet. Those two scenarios with the gun depend on him not wasting the bullet. If he did, then we just leave the gun there, and get medical help for anyone if that bullet went into them. After this is done, we can do whatever paperwork/legal BS from there after we call the cops and tell them what happened.
Not trying to be ITG, it's just...Five to one man! C'mon!!