This is at 25NL.
We both have almost exactly $25.
No read on this guy other than he seems to bet a lot in position. Not sure if he has had the goods or not.

Hero delt :Ah: :Kd: in CO I raise to $1.00

SB calls and one limper I have position on all of them.

Flop is :Ks: with pot at $3.25
Both check to me I bet $2.50
SB calls, limper folds.

Turn is pot = $8.25
Check to me I bet $6.00
SB calls.

River is
SB goes allin for $14

I am stumped. Is this an laydown or call?
Part of me says this is a bluff but the other half says that he hit
and is part of the "ALLIN WHEN I HAVE THE NUTS" group.