Need some help on this one.. villain has played fairly agressively, many pot-sized bets and some huge overbet allin's, none of which have been called.

6-Max NL 400 on Pacific
Lukie: $545
Villain (CO): $444

Lukie dealt KK in SB.
UTG and UTG+1 fold.
CO min-raises to $8.
Lukie reraises to $22 total.
BB folds.
CO calls.

Flop: 4c 2c 6d

Lukie bets $30.
CO calls.

Turn: 4c 2c 6d 3h

Lukie checks.
CO bets $29.
Lukie calls.

River: 4c 2c 6d 3h Js
Lukie bets $40.
CO goes all-in.
Lukie folds.

I'm interested how you guys would have played this, especially on the turn and river. I'm thinking the villain sensed weakness in the check/call on the turn and 1/4 sized bet on the river and pushed on a bluff. It could have also easily been a preflop steal with 5x and he could have had the straight. Thoughts?

- Lukie