nl100, strange river with AA

[Frawa]

Poker Stars, $0.50/$1 NL Hold'em Cash Game, 6 Players
LeggoPoker.com - Hand History Converter

UTG: $129
MP: $80.50
CO: $49.20
Hero (BTN): $110.50
SB: $25.50
BB: $101.50

Pre-Flop: A[img]/images/graemlins/diamond.gif[/img] A[img]/images/graemlins/club.gif[/img] dealt to Hero (BTN)
3 folds, <font color="red">Hero raises to $4</font>, SB folds, BB calls $3

Flop: ($8.50) Q[img]/images/graemlins/heart.gif[/img] 3[img]/images/graemlins/spade.gif[/img] T[img]/images/graemlins/diamond.gif[/img] (2 Players)
BB checks, <font color="red">Hero bets $6</font>, BB calls $6

Turn: ($20.50) 4[img]/images/graemlins/heart.gif[/img] (2 Players)
BB checks, <font color="red">Hero bets $16.50</font>, BB calls $16.50

River: ($53.50) 9[img]/images/graemlins/spade.gif[/img] (2 Players)
<font color="red">BB bets $75 and is All-In</font>, Hero ???

villain is 30/6.7/1

who calls + why?