Fold. You still have a lot of chips left over, and it is not worth risking. Since you dont know this guy, you could say he has a peice of the flop, but not a big one and is just bullying the shorter stack because he knows they will most likely fold because they are so close to the money. But he could also be holding a set, 2 pair, or over cards. You did not commit yourself enough to this pot and you still have 30bb's so just fold and wait for a better spot.