AK flopped trips with lots of aggression

[Peter]

I joined the open challenge for december and I promised to post more hands so that the person who is matched with me will actually see his choice of avatar for me when he wins.
Here's a hand from about a month ago.

5/10 6 max at Party.

I'm UTG and raise A [img]/images/graemlins/diamond.gif[/img]K [img]/images/graemlins/diamond.gif[/img], button coldcalls and the SB calls as well. Both opponents didn't seem to get extremely out of line for the time I had been at the table.

Flop: K [img]/images/graemlins/spade.gif[/img]K [img]/images/graemlins/heart.gif[/img]5 [img]/images/graemlins/heart.gif[/img]

I bet, button raises, SB 3 bets and I cap. Both call.

Turn: 6 [img]/images/graemlins/diamond.gif[/img]

I bet, button raises, SB coldcalls, I 3bet and button caps. SB calls.

River: 8 [img]/images/graemlins/heart.gif[/img]

SB bets, I call, button raises, SB 3bets, I fold, button caps, SB calls.

Who backs off earlier, who calls down? And why?

Peter