Look at the hand from Villain's perspective. He limped UTG and then the action went: minraise, 3-bet, cold call, and regardless of this he still put in a 4-bet with three live players behind him who have all shown strength. Furthermore, his 4-bet is small and doesn't even look like he's trying to take the pot down now or to at least narrow the field significantly. He's telling you he has AA or MAYBE KK. Clear fold.