River decision with AK: snap call or fold?

[J_C]

***** Betfair Poker Hand History *****
NL $2.50/$5 Texas Hold'em
Table Nitrogen 02 6-max (Real Money)
Seat 3 is the button
Total number of active players : 5
Seat 1: bootsylad ( $385.90 )
Seat 2: H0lden123 ( $938.50 )
Seat 3: Softiiich ( $674.65 )
Seat 4: BajenFan ( $907.90 )
Seat 5: Poker1976 ( $634.65 )
Seat 6: Hero ( $860.08 )
Poker1976 posts small blind [$2.50]
Hero posts big blind [$5]
** Dealing down cards **
Dealt to Hero [ Kd, Ad ]
bootsylad folds
H0lden123 folds
Softiiich raises to [$17.50]
Poker1976 calls [$15]
Hero raises to [$70]
Softiiich calls [$52.50]
Poker1976 calls [$52.50]
** Dealing Flop ** [ Ks, 7c, 5s ]
Poker1976 checks
Hero bets [$140]
Softiiich calls [$140]
Poker1976 folds
** Dealing Turn ** [ 3s ]
Hero checks
Softiiich checks
** Dealing River ** [ 9c ]
Hero checks
Softiiich goes all-in
Softiiich bets [$464.65] (pot about $487 at this point)

Hero ?

Softiich is 26/10/5 on a 200 hand sample size before the hand, although the AF figure surprises me as I didn't feel him to be that aggressive. Poker1976 seems loose preflop and passive postflop. The table is generally playing fairly loose and only moderately aggro. I am playing 25/20/3ish.

Did I just induce a bluff/misjudged value bet from a worse K or, given that my hand is virtually face up, is this usually AA, set or flush trying to get value? I think AA is less likely (since a flop shove would be the obvious move) but the flat call on the flop with a player to come looks either very scary or a loose call with a draw.