Live 5-table tourney A6s with paired board

[WJL]

Playing in a live 50-man rebuy tournament with about 15-minute blind levels. First break and rebuy period over, I am playing TAG and have been a little up and down; stack at 850 (opened at 750). Tourney breaks to 4 tables and I am on about the 3rd hand on new full 10-man table with no reads. Blinds are 25/50, soon to move to 50/100. Villain has slightly shorter stack UTG.

Preflop: Hero is in CO with A[img]/images/graemlins/diamond.gif[/img] 6[img]/images/graemlins/diamond.gif[/img]
7 players limp in, including Hero.

Flop: (t350) 10[img]/images/graemlins/club.gif[/img] 6 [img]/images/graemlins/heart.gif[/img] 10 [img]/images/graemlins/spade.gif[/img]
table checks to Hero, raises 200; 2 folds, villain calls, 3 folds

At this point I have a strong feeling that the Villain does NOT have a 10; told me he was calling my bluff.

Turn: (t750) K [img]/images/graemlins/diamond.gif[/img]
Villain checks, Hero checks

River: (t750) A [img]/images/graemlins/spade.gif[/img]
Villain checks, Hero raises 100, Villain raises to 300, Hero?