Villan caps the river - bluff or value bet?

PokerStars Limit Hold'em, $2.00 BB (8 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

Preflop: Hero is MP2 with Q, Q
UTG raises, 2 folds, Hero 3-bets, CO calls, 3 folds, UTG calls

Flop: (10.5 SB) J, 7, Q (3 players)
UTG checks, Hero bets, CO calls, 1 fold

Turn: (6.25 BB) 6 (2 players)
Hero bets, CO calls

River: (8.25 BB) J (2 players)
Hero bets, CO raises, Hero 3-bets, CO caps, Hero calls

Total pot: $32.50 (16.25 BB) | Rake: $1

Results in white below:
Hero had Q, Q (full house, Queens over Jacks).
CO had A, K (one pair, Jacks).
Outcome: Hero won $31.50