10NL:Weak Overpair

I knew nothing about this guy and his river bet was weird. Whaddaya think?

MP2 ($9.75)
MP3 ($8.75)
Hero ($9.55)
Button ($8.75)
SB ($11)
BB ($10)
UTG ($20.45)
UTG+1 ($21.40)
MP1 ($12.80)

Preflop: Hero is CO with 8, 8.
2 folds, MP1 calls $0.10, 1 fold, MP3 calls $0.10, Hero calls $0.10, 2 folds, BB checks.

Flop: ($0.45) 6, 7, 4 (4 players)
BB checks, MP1 checks, MP3 checks, Hero bets $0.45, BB folds, MP1 folds, MP3 calls $0.45.

Turn: ($1.35) 2 (2 players)
MP3 checks, Hero bets $0.75, MP3 calls $0.75.

River: ($2.85) K (2 players)
MP3 bets $3, Hero calls $3.

Final Pot: $8.85

raise preflop, as played fine

weird spot. Limping range of an unknown at 10nl is huge. You need to be ahead >1/3 of the time for calling to be +EV, I guess that it's close enough here that calling is ok (my instinct is to fold without at least some read though)

tough spot imo...i would have to fold to the river bet thinking he has Ac5c, K7s or a set.
did he have one of those?

becuase there was no raise preflop, I prefer to check the turn and keep the pot small. My thinking is that our hand is weak really and becuase there was no raise they could have nearly anything with 2pair and sets reasonably high on their list of possible holdings. I don't see any hands we beat apart from bluffs that want to play for a big pot. If you know nothing about this person I'm folding that river the majority of the time as bluffing doesnt seem to make sense in this spot to me.

raise preflop fold river. NH in the middle