Without a read make the call. Given you saw him do that later with a boat, it seems likely that he did have you beat and you should keep that in mind if you play against him later. Some players are like that - hair-trigger all-ins if they have a strong hand, and they hope people will call often enough to profit from it.

preflop raise was weak.
Pre-flop raise is fine, and seeing the flop with two others is fine. Kings aren't such a shrinking violet that you have to chase off all action.