"careful, don't go broke now"

[mikech]

bellagio 10-20. old guy directly to hero's right is making the game very live. he had like a 10k stack, lost all but 2k of it, but now has gotten back to about 10k, all within the past hour. he opens to 100 from ep, hero makes it 300 with JJ, hu to the flop which comes AJ3, all clubs. old guy checks, hero bets 500, old guy calls. turn is an os K, check, bet 1200, call. river an os 5, check, hero starts counting down his chips and bills, which total around 5k (old guy covers), when the old guy suddenly says, "careful, don't go broke now."

hero does what?