You should have raised the flop, probably to potsized raise, than you see where you are, if you're faced with an all in, than it's tough, I would probably call, but it could be possible that he had JJ, TT...
Against the range of 99+, AKo, AKs, you've got a 72% equity on that flop, so an all in on the flop is a no brainer call.
Against a range of TT+ you still have a 62% equity...calling an all in is still actual.