Help with this hand analysis, please

[shish]

EDITED to show turn bet****

Indian Casino daily tournament. Insane blind structure. I only play these sometimes to get more live experience, I know it's mostly a crapshoot since the blinds go up every 15 minutes. Buyin is 20, no rebuys, and $5 bounties.

I have 8000 chips

Villian has approx. 11000. I'm on the button, blinds are 300/600. Villian is BB. A raise to 15-1800 is taking the blinds on most hands. I've built my stack playing agressive, only getting in big pots where I have a solid hand. I've been doing my share of stealing, but haven't gotten caught yet. Villian has played several big pots, each of which he didn't have a great hand, but flopped well. He played agressively after he hit the flop. Seems like a solid player, but I haven't played with him enough to have a good read, other than he plays a lot of hands.

It gets folded around to me on the button. I pick up A [img]/images/graemlins/diamond.gif[/img]7 [img]/images/graemlins/diamond.gif[/img]. Not a great hand normally, however since the blinds go up so fast, you can't wait for a premium hand, nobody yet to act looks too interested, and I decide to steal the blinds. I raise to 1800. The blinds both call, which is not what I was expecting. So I'm looking for a good flop, but not too excited about the hand. The SB only has about 2000 left after the call.

Flop is AQ5 rainbow. I'm not too sure if my ace is good here. I think they more than likely have one of the following hands:

Small PP (if it was a high pocket pair, I think they would have reraised with the fast structure)
Big Ace
Ax suited
Two big cards with no ace.

They check the flop, I thought about firing out to try and steal the pot, but I thought I was likely ahead and I thought I'd try and trap. Most of the table had been playing fairly straightforward. If nobody had anything, it would get checked down very often. I was still wary of someone with a bigger ace than mine maybe thinking the same thing.

The turn was a King of hearts putting 2 hearts on the board. Check, check, I fire out 2000 fairly quickly. The SB was folding while I was putting my bet out. The BB IMMEDIATELY says All In. My first instinct was to call thinking that he had something like KT, KJ, or KQ. Or that he had made up his mind to push before I even bet, maybe he sensed weakness in me and thought I was trying to buy the pot.

I folded after about a minute. I didn't want to risk my whole tournament on a hand that I could very well be dominated on. However, the way I played the hand, I thought I was ahead and wanted him to put his chips in. I must say the instant all in really shocked me. The money was fairly far off, and doesn't really come into play at this point.

Was this a horrible fold? Also, if someone can help me out, can you please do a range of hands for villian based on the info I gave? I have HOH and have read it 4 times, I'm trying to get better on narrowing down range of hands and I would really appreciate it if someone could write down how they would think about this hand.

Thanks for any and all input.