Strange step 5 hand with Gigabet

[DrGonzo]

This hand was played a few days ago, in the beginning of a step 5 tournament. I know Giga is a very good player, but I can't see his thinking behind this play. Can you?

Party Poker No-Limit Hold'em Tourney, Big Blind is t15 (10 handed) converter

saw flop|<font color="#C00000">saw showdown</font>

<font color="#C00000">UTG+1 <font color="#A500AF">(Slon_T)</font> (t1210)</font>
Hero (t970)
MP1 (t900)
MP2 (t975)
MP3 (t970)
CO (t1000)
<font color="#C00000">Button <font color="#A500AF">(Gigabet)</font> (t870)</font>
SB (t1105)
BB (t1000)
UTG (t1000)

Preflop: Hero is UTG+2 with A[img]/images/graemlins/diamond.gif[/img], 2[img]/images/graemlins/club.gif[/img].
UTG folds, <font color="#CC3333">UTG+1 <font color="#A500AF">(Slon_T)</font> raises to t125</font>, Hero folds, MP1 folds, MP2 folds, MP3 folds, CO folds, Button <font color="#A500AF">(Gigabet)</font> calls t125, SB folds, BB folds.

Flop: (t275) K[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/heart.gif[/img], 6[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Slon_T bets t1085 (All-In)</font>, Gigabet calls t745 (All-In).

Turn: (t2105) A[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players, 2 all-in)</font>

River: (t2105) 2[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players, 2 all-in)</font>

Final Pot: t2105

Results in white below: <font color="#FFFFFF">
Slon_T has 2h 2s (full house, twos full of kings).
Gigabet has 5s 6c (two pair, kings and sixes).
Outcome: Slon_T wins t2105. </font>

It turned out that the guy he was playing against was a pretty reckless player. This was in the beginning of the tourney, but Giga could have had notes on him of course. I still don't see a reason to call the preflop raise with 56. Even if you hit the flop and the guy checks, you can't know if you have him beat.

I would really like to hear your ideas about this [img]/images/graemlins/smile.gif[/img]. Thx!