Dassey said the two went to Avery's bedroom where Dassey saw Halbach naked -- shackled to the bed with handcuffs and leg irons -- and begging for help, the complaint said.

Dassey said he raped a crying Halbach as she pleaded with him to uncuff her, to "tell Steve to knock it off" as Avery watched nearby, the complaint said.

Afterward, Dassey said he and Avery left the bedroom and watched television.

Dassey said Avery told him, "That's how you do it," the complaint said. Dassey stated that Avery told him he did a good job and he was proud of him.

Halbach killed

Avery then stabbed Halbach in the stomach with a 6- to 8-inch kitchen knife and told Dassey to slit her throat, which he did, the boy told investigators. The uncle also told Dassey to cut some of her hair, the complaint said.

Halbach was still alive so Avery strangled her for two to three minutes, washed his hands, then punched her and told her to "shut up," the complaint said.

The two unshackled her, tied her up with rope and carried her to the detached garage, the complaint said. Avery then shot her about 10 times on the garage floor with a .22-caliber rifle, the complaint said.