1st hand in 5 table SNG. Blew off a chunk of my stack right way. At what point did I make my biggest mistake?

PokerStars No-Limit Hold'em Tourney, Big Blind is t20 (9 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

Button (t1500)
SB (t1500)
BB (t1500)
UTG (t1500)
UTG+1 (t1500)
Hero (t1500)
MP2 (t1500)
MP3 (t1500)
CO (t1500)

Preflop: Hero is MP1 with T, A.
2 folds, Hero raises to t60, 1 fold, MP3 calls t60, CO raises to t120, 3 folds, Hero calls t60, MP3 calls t60.

Flop: (t390) 2, 4, 2 (3 players)
Hero bets t300, MP3 calls t300, CO raises to t1380, Hero folds, MP3 folds.

Final Pot: t2370