2/4 6max: Standard line with AA vs unknown

[Pokerstuff2]

I know my bet was too small on flop. Too many callers prefop, then a huge check raise from unknown this has to be a set?

Poker Stars, $2/$4 NL Hold'em Cash Game, 5 Players
LeggoPoker.com - Hand History Converter

SB: $989
BB: $660.10
Hero (UTG): $400
CO: $396.20
BTN: $72

Pre-Flop: A[img]/images/graemlins/spade.gif[/img] A[img]/images/graemlins/heart.gif[/img] dealt to Hero (UTG)
<font color="red">Hero raises to $16</font>, CO calls $16, BTN folds, SB calls $14, BB calls $12

Flop: ($64) 5[img]/images/graemlins/heart.gif[/img] 8[img]/images/graemlins/club.gif[/img] T[img]/images/graemlins/heart.gif[/img] (4 Players)
SB checks, BB checks, <font color="red">Hero bets $32</font>, CO folds, <font color="red">SB raises to $124</font>, hero?