You missed a vital point manifest, he was raising pre flop in the worst position with AT!!

Your pre flop raise wasn't enough either, I assume raising with AT you didnt actually want to see a flop, a raise of that size isn't enough to steal with that many limpers.

At most you should be flat calling with this and checking even if you hit the ace (from 1st position) or putting out a small feeder bet. If you get called and they show strength on the turn without you hitting 2 pair, you're behind and you muck your cards. If you check you can make a small call and see how they play the turn (or try and hit 2 pair).