The way I looked at it, either he had aces, a drawing hand, or worse, BOTH.
Based on his flat call to my preflop raise, I"ve put him on a drawing hand. Probably flush, unlikey to be straight, but who knows.
My options are :-
Check. Do I want to give him a free card ? Or if he bets, am I calling ?
Raise. With 9k back, pot of 7k, I"m effectively committing myself with any reasonable raise.
All-In. Can he call if he"s drawing ? Is he already ahead ?