donk bets confuse me: AA in BB

[linuxrocks]

Villian is running at 30/16.7/0.5. Haven't seen him bet so big on the river and with his aggression, it felt like this can't be a bluff. But, I can beat a king. Question is: how often does he have two pair or better (like a flush)?

PokerStars No-Limit Hold'em, $4 BB (5 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

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

UTG ($783)
MP ($448)
Button ($1206.45)
SB ($589.35)
linuxrocks ($641.35)

Preflop: linuxrocks is BB with A[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">3 folds</font>, <font color="#CC3333">SB raises to $8</font>, <font color="#CC3333">linuxrocks raises to $36</font>, SB calls $28.

Flop: ($72) K[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/diamond.gif[/img], T[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets $4</font>, <font color="#CC3333">linuxrocks raises to $68</font>, SB calls $64.

Turn: ($208) 8[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets $16</font>, linuxrocks calls $16.

River: ($240) 2[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets $169.35</font>, linuxrocks ??.

Final Pot: $240