Tricky one I think.
I reckon the 1st guy has Kings. In fact I'm pretty darn sure. Queens at the very least. He probably wouldn't go all-in with jacks. I have the ad so he doesn't have ad kd.
Not too sure what the second guy has. True, the smooth call is very suspicious, but this could also mean he has the flush draw and is trying to get value by luring me in. Once again I have the ad, which narrows his options, but there's no reason why he can't have a hand like kd qd or jd td. It is online don't forget.

Could the caller be holding a set? Not sure. I doubt he'd call preflop with

or

, but maybe he'd be tempted with

. If so, then at least I'd have the backdoor flush draw and 2 live aces to hit. Not sure that's enough to warrant a call though.
He could certainly have an overpair. Kings are unlikely if the all-in holds them. He may have queens, but I'm not sure he'd flat call the original raise. - even if the raise to 4 is suspicious. Jacks is a definite option. Tens less so, but players online do sometimes struggle to lay hands down.
If I am to play this hand, I believe I must move all-in. If he has me beat, then he's going to bet on the next street anyway, and I'll be too pot committed to fold. If he has a draw, I don't want to give him a chance to fold on the turn or river. Calling's not an option in my book.
Hmm. Still not sure what the best play was...
(Could do with some words of wisdom from Ironside

)