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