AK...how's my line?

[coolmoedee]

Absolute Poker
No Limit Holdem Ring game
Blinds: $1/$2
6 players
Converter

Stack sizes:
Hero: $301.53
UTG+1: $485
CO: $263.30
Button: $182.95
SB: $394.80
BB: $279.95

Pre-flop: (6 players) Hero is UTG with A K
Hero raises to $8, UTG+1 calls, 3 folds, BB raises to $26, Hero calls, UTG+1 calls.

Flop: A T 8 ($79, 3 players)
BB checks, Hero bets $55, UTG+1 folds, BB calls.

Turn: 2 ($189, 2 players)
BB checks, Hero pushes all in?

Not sure what to do here? My thought was that he had something like KK but why even call the flop bet? Not sure if aggression or passiveness is the play here. Thoughts appreciated.