NL100: Weird spot with nut straight

[Artsemis]

Poker Stars - No Limit Hold'em Cash Game - $0.50/$1 Blinds - 8 Players - (LegoPoker Hand History Converter)

SB: $21.25
Hero (BB): $111.35
UTG: $54.85
UTG+1: $43.45
MP1: $93.00
MP2: $106.00
CO: $65.35
BTN: $54.25

Preflop: Hero is dealt A[img]/images/graemlins/diamond.gif[/img] J[img]/images/graemlins/diamond.gif[/img] (8 Players)
UTG folds, UTG+1 calls $1.00, 3 folds, BTN calls $1.00, SB folds, Hero checks

Flop: ($3.50) 3[img]/images/graemlins/diamond.gif[/img] Q[img]/images/graemlins/heart.gif[/img] K[img]/images/graemlins/club.gif[/img] (3 Players)
Hero checks, <font color="red">UTG+1 bets $1.00</font>, BTN calls $1.00, Hero calls $1.00

Turn: ($6.50) T[img]/images/graemlins/club.gif[/img] (3 Players)
Hero checks, UTG+1 checks, <font color="red">BTN bets $5.00</font>, <font color="red">Hero raises to $10.00</font>, UTG+1 folds, BTN calls $5.00

River: ($26.50) 9[img]/images/graemlins/club.gif[/img] (2 Players)
<font color="red">Hero bets $10.00</font>, <font color="red">BTN raises to $30.00</font>, Hero ???