weird river spot $400nl

[ianisakson]

PokerStars No-Limit Hold'em, $4 BB (7 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

UTG ($362.60)
Hero ($539.20)
MP2 ($287)
CO ($301.95)
Button ($480.35)
SB ($431)
BB ($564.25)

Preflop: Hero is MP1 with A, K.
[color=#666666]1 fold</font>, [color=#CC3333]Hero raises to $12</font>, [color=#666666]3 folds</font>, SB calls $10, [color=#666666]1 fold</font>.

Flop: ($28) 2, 3, 7 [color=#0000FF](2 players)</font>
SB checks, Hero checks.

Turn: ($28) 3 [color=#0000FF](2 players)</font>
[color=#CC3333]SB bets $16</font>, [color=#CC3333]Hero raises to $48</font>, SB calls $32.

River: ($124) K [color=#0000FF](2 players)</font>
[color=#CC3333]SB bets $4</font>, [color=#CC3333]Hero raises to $108</font>, [color=#CC3333]SB raises to $371</font>, Hero ??????


Should I have just called the river min-bet?
Do I have to call now?
What does my hand look like if you're Villain?