BIGGGGG river overbet at $3/$6

[The NorthenStar]

Sup guys, this just happened at $3/$6 on ipoker. Defo interested as to what u guys think.
No major reads on villan, he has been quiet though, not in many pots. We havent played a pot until now. I have been playing 21/16 over small sample. Effective stacks are $575:

Hero is UTG, Villan is in the SB:
** HOLE CARDS ***

Dealt to hero[H5 D5]
hero: Raise $21.00
UTG+1: Fold
BTN: Fold
Villan: Call $18.00
BB: Fold
*** FLOP *** [SJ C5 D9]
Villan: Check
Hero: Bet $30.00
Villan: Call $30.00
*** TURN *** [H4]
Villan: Check
Hero: Bet $58.00
Villan: Call $58.00
*** RIVER *** [S6]
Villan: Allin $464.35
Hero: [img]/images/graemlins/confused.gif[/img]
*** SUMMARY ***

Thoughts on heros line before river of course welcome. Hero does what on river? What are you putting villan on as a result of his line too plz. Many thanks, results to follow.