C/R'd on river by LAG

Villain is 42/11/3.8 No reads.
PokerRoom No-Limit Hold'em, $0.5 BB (5 handed) converter

<font color="#C00000">Hero ($54.90)</font>
Button ($45.25)
SB ($25.05)
<font color="#C00000">BB ($42.45)</font>
UTG ($194.45)

Preflop: Hero is MP with K[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/heart.gif[/img].
UTG calls $0.50, Hero calls $0.50, <font color="#666666">1 fold</font>, SB completes, BB checks.

Flop: ($2.50) 7[img]/images/graemlins/spade.gif[/img], 3[img]/images/graemlins/heart.gif[/img], 2[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, BB checks, UTG checks, <font color="#CC3333">Hero bets $2</font>, SB folds, BB calls $2, UTG folds.

Turn: ($6.50) 9[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">BB bets $2</font>, Hero calls $2.

River: ($10.50) 9[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
BB checks, <font color="#CC3333">Hero bets $4.5</font>, <font color="#CC3333">BB raises to $19</font>, Hero?

I put him on hearts, 9's full, or trips. Since he made the flop call, x9 seems less likely than the others. The river C/R is very bad if he doesn't have the full house. I'm getting 34/14.5 = 2.3:1

Is this a fold or a crying call?
Do you check behind on the river?
Any other comments appreciated as well.