Is this call read dependant?

[JL]

Villain is unkown
His river bet just screamed bluff at the time.
Is this a good or bad call vs an unkown?

PokerRoom No-Limit Hold'em, $1 BB (5 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

MP ($48.00)
Button ($53.00)
Hero ($107.10)
BB ($105.50)
UTG ($38.70)

Preflop: Hero is SB with 9, 9.
3 folds, Hero raises to $3.5, BB calls $2.50.

Flop: ($7) 8, T, T (2 players)
Hero bets $5, BB calls $5.

Turn: ($17) 3 (2 players)
Hero bets $10, BB calls $10.

River: ($37) K (2 players)
Hero checks, BB bets $28, Hero calls.....????

Final Pot: $93

[IowaSkinsFan]

I think this is an easy call. Even versus an unknown.