5-4 gets into trouble on river

5/10 nl lads 6max

hero´s stacksize 1500$
co´s stacksize 1100$

hero´s on button with 5-4 [img]/images/graemlins/spade.gif[/img]

utg folds
co calls for $10
hero raises to $40
sb folds
bb folds
co calls for $30

Flop comes 5 [img]/images/graemlins/heart.gif[/img]5 [img]/images/graemlins/club.gif[/img]10 [img]/images/graemlins/diamond.gif[/img] (95$)

co checks
hero bets $60
co calls $60

turn 2 [img]/images/graemlins/spade.gif[/img] (215$)

co checks
hero bets $100
co calls $100

river 3 [img]/images/graemlins/diamond.gif[/img] (415$)

co bet $500

what´s my move here?
has he been slowplaying a monster all the way or is he on a complete bluff? is folding obvious?

the only thing I knew about this guy who recently sat down was that he went allin preflop with A-10o with 200$ against my friends AA 5min ago on 1/2 nl