Villain is new at table, less than 5 hands since his arrival so no reads. Hero stats for session 14/11 over 50ish hands, not been out of line, only gone to showdown with the goods so far.

I think Villains passive c/call line on flop/turn usually means he's chasing the FD here. Or possibly slow playing a set of 6s/Ts. How often is villain shoving this river with less than a set/flush? Is this an easy fold with bottom set, or is villain just as likely bluffing that he hit the flush and has something like KT or worse?

PokerStars Game #18678515411: Hold'em No Limit ($0.10/$0.25) - 2008/07/08 - 17:29:20 (ET)
Table 'Fricke' 9-max Seat #2 is the button
Seat 1: steez38 ($27.75 in chips)
Seat 2: timmyd305 ($7.05 in chips)
Seat 3: serif13 ($14.65 in chips)
Seat 4: Gloubiboulga ($21.30 in chips)
Seat 7: KILR MILR11 ($16.45 in chips)
Seat 8: temmikongi ($24.65 in chips)
Seat 9: LordVFR ($33.40 in chips)
serif13: posts small blind $0.10
Gloubiboulga: posts big blind $0.25
gustav1234: sits out
afterchrist: sits out
*** HOLE CARDS ***
Dealt to LordVFR [4c 4s]
KILR MILR11: folds
temmikongi: folds
LordVFR: raises $0.75 to $1
steez38: folds
timmyd305: folds
serif13: calls $0.90
Gloubiboulga: folds
*** FLOP *** [6c Kd Tc]
serif13: checks
LordVFR: bets $1
serif13: calls $1
*** TURN *** [6c Kd Tc] [4d]
serif13: checks
LordVFR: bets $2.75
serif13: calls $2.75
*** RIVER *** [6c Kd Tc 4d] [3c]
serif13: bets $9.90 and is all-in
Hero????

BTW, I know flop cbet too small, was running out of time as multi tabling and misclicked the bet slider.