(6/19/2018) - A 22-year-old is behind bars, accused of engaging in a "sadistic torture relationship" with a 13-year-old who ran away from home three years ago.

The girl was located during a countywide sweep last week in which police found 51 of 76 missing juveniles. She later gave graphic accounts to police of the way 22-year-old Derek Sewell treated her.

"This is the guy that inflicted torture and imprisonment on a young 13,14,15-year-old child," said Genesee County Sheriff Robert Pickell.

Sewell moved in with the girl's parents when she was 13, according to Pickell. Soon after, Sewell and the girl started having a sexual relationship in the home.

He moved out and she ran away to live with him. They continued living together on the run for the next three years, while Sewell engaged in what Pickell called a "sadistic torture relationship" with the girl.

"We don't know as of this time that he ever human trafficked her, but the relationship was one of a sadistic nature," Pickell said.

Pickell said Sewell threatened to kill the girl multiple times. He allegedly held her head and neck underwater once and held a microwave over her head another time.

Sewell also allegedly physically abused the girl on a daily basis. At one point, Pickell said Sewell cut her feet and thighs with a knife.

"She said she was always in fear of her life," he said.

The girl was able to finally escape and run back to her parent’s home about two weeks ago.

Police located the girl at her parents' house last week during the countywide sweep, which involved 70 officers from most law enforcement agencies in Genesee County raiding several locations.

Pickell said the girl, who is now 16, is receiving therapy to begin healing from the three-year ordeal.

Sewell has been arrested and arraigned on eight criminal charges, five of which carry a maximum sentence of life in prison:

-- Three counts of first-degree criminal sexual conduct with a victim age 13 or younger and the suspect age 17 or older.

-- First degree criminal sexual conduct.

-- Attempted murder.

-- Unlawful imprisonment.

-- Two counts of assault with intent to do great bodily harm.

Police are investigating four to six cases of possible human trafficking stemming from last week's sweep. Charges had not been announced against any other suspects by Tuesday.