Looks to me like he just made two-pair or a straight. AJ, KQ and JTs all fit his play very well. KQ gives him the nuts on the river, and the other two are close enough to it heads-up to justify the push.
But of course a bluff is always a possibility - suited connectors also fit his play well - so look at the pot odds. 54 into 87 means you need him to be bluffing well over 1/3 of the time. I don't see it - not with that sizing. Plus you are putting your life at risk in a completely uncertain situation, very early in a tournament. Just be patient: sooner or later some fish will put all their chips in the pot when you're sure that you're ahead. (Quite possibly this fish, if he's bluffing all his chips in this spot
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Would people call a half-pot-sized bet here? That would be much more difficult for me to fold to, since (a) the pot odds mean I only need a 1-in-4 chance of a bluff; (b) I'm not risking my life; and (c) the bet size in itself makes a bluff more likely (he's not risking his life either). With the sort of loose player you describe, I'm probably calling and praying it's a busted FD or KJ (which is another very plausible holding for him). I'm not loving it though
- an A is just so so likely here, since plenty of fish will raise any A in any position pre-flop. I reckon I'm folding even to a 17BB bet if this is the first pot I've seen him really go for.