I'm SB, MP2 has J9s. What is going on here?

Party Poker No-Limit Hold'em, $ BB (10 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

saw flop|saw showdown

CO ($27.80)
Button ($34.35)
SB ($23.65)
BB ($22.98)
UTG ($49.10)
UTG+1 ($50.68)
UTG+2 ($8.75)
MP1 ($19.99)
MP2 ($21.50) :Jc:
MP3 ($14.65)

Preflop: SB posts a blind of $0.10.
4 folds, MP2 calls $0.25, 3 folds, SB (poster) raises to $1, 1 fold, MP2 calls $0.75.

Flop: ($2.25) 5, Q, J (2 players)
SB bets $1.5, MP2 calls $1.50.

Turn: ($5.25) 5 (2 players)
SB checks, MP2 bets $3, SB raises to $8, MP2 raises to $13, SB calls $5.

River: ($31.25) 2 (2 players)
SB checks, MP2 checks.

Final Pot: $31.25

I want your oppinions on what went on in this guy's head during this hand.