Stacked Deck?

Home poker game, $50 buy in, 1-2 NL. Dealer is the resident of the house and he has a friend who is SB. Here is the hand: UTG calls, all fold to CO who raises to $5. SB calls, BB Calls (4 players).

Flop comes Ah Qh 8c

SB bets $5
BB raises to $10
UTG calls $10
CO raises to $25
SB goes all in $125
BB goes all in for $200
UTG goes all in for $100
CO calls all in for $150.

SB has 8s 8d
BB has Qs Qc
UTG has Kh Jh
CO has As Ac.

At this point all three players hit a set on the flop, and the UTG had a nut flush draw, a nut straight draw, and a royal flush draw.

Turn card is an 8h, giving an Aces full full-house, a Queens full full-house, a nut flush, and quads. River is a blank.

My point is the winner with quads was the dealers friend, and seemed pretty shady. once i saw that hand i got up and left the table, because he just won a $400 hand, when most pots were $40 all night. Now I am curious about the game and if there is cheating. What i am wondering is what you can look for to 'know' folks are cheating/colluding.