Should I not have pushed here?

[lonn19]

The guy that called me was playing on the aggressive side once he became chip leader. After the flop, I thought chances were that he did not have a pair, so I moved all in. Turned out to be a bad decision. Was I right to take the chance or should I have let it go after the flop, possibly check folding?
PokerStars Game #3192854096: Tournament #15799716, Hold'em No Limit - Level IV
(50/100) - 2005/11/29 - 14:22:37 (ET)
Table '15799716 1' Seat #1 is the button
Seat 1: egyptianmusk (3910 in chips)
Seat 2: blakes76 (1770 in chips)
Seat 5: jstnhager (2270 in chips)
Seat 6: no_Englishs (1830 in chips)
Seat 7: Hermundur (2565 in chips)
Seat 8: grossguy (1155 in chips)
blakes76: posts small blind 50
jstnhager: posts big blind 100
*** HOLE CARDS ***
Dealt to grossguy [Ah Kd]
no_Englishs: folds
Hermundur: calls 100
grossguy: raises 200 to 300
egyptianmusk: calls 300
blakes76: folds
jstnhager: folds
Hermundur: folds
*** FLOP *** [7s 7c 4c]
grossguy: bets 855 and is all-in
egyptianmusk: calls 855
*** TURN *** [7s 7c 4c] [5c]
*** RIVER *** [7s 7c 4c 5c] [8c]
*** SHOW DOWN ***
grossguy: shows [Ah Kd] (a pair of Sevens)
egyptianmusk: shows [Qs Qc] (a flush, Queen high)
egyptianmusk collected 2560 from pot
*** SUMMARY ***
Total pot 2560 | Rake 0
Board [7s 7c 4c 5c 8c]
Seat 1: egyptianmusk (button) showed [Qs Qc] and won (2560) with a flush, Queen
high
Seat 2: blakes76 (small blind) folded before Flop
Seat 5: jstnhager (big blind) folded before Flop
Seat 6: no_Englishs folded before Flop (didn't bet)
Seat 7: Hermundur folded before Flop
Seat 8: grossguy showed [Ah Kd] and lost with a pair of Sevens