Fadden, 39, was a convicted sex offender and rapist who was about to stand trial on Monday when he carried out the killings before turning the gun on himself.
Families of the two teenage victims were allowed on the property where they witnessed a horrific scene.
A dog collar, handcuffs, drug paraphernalia, and weapons were strewn across the laundry room. The house was littered with syringes filled with unknown substances.
Holly Guess, 35, who was married to McFadden, and her three children, Rylee Elizabeth Allen, 17; Michael James Mayo, 15; and Tiffany Dore Guess, 13, were all found slain on the property of McFadden's rural Oklahoma home.
Ivy Webster, 14, and Brittany Brewer, 16, who had visited the home for a sleepover, who were also found dead at the house.