An 8-year-old Pennsylvania boy who was hospitalized with life-threatening injuries Monday has died, and his mother's fiancé was arrested.

The medical examiner told WPXI on Thursday evening that he had been called to Children's Hospital of Pittsburgh to recover the child's body.

Detectives from the Allegheny County Police Department said the boy was taken to a hospital Monday by a family member. Doctors then called police.

According to a criminal complaint obtained by WPXI, doctors said the boy, later identified as JohnMarquis Stepich, was placed on a ventilator and had a brain bleed as well as a herniated brain stem and bruises all over his body. He was pronounced dead Thursday afternoon.

Police arrested Orlando Williams, 38, late Monday night. He is facing charges of aggravated assault, endangering the welfare of a child and recklessly endangering another person.

Williams remained in the Allegheny County Jail as of Thursday evening.

The complaint said Williams told police he had been drinking earlier in the day Sunday and that his fianceé left for work, leaving him with her three children. Williams told police that while in JohnMarquis’ room, he stumbled on a laundry basket with clothing inside. Williams said he became angry and yelled at the boy.

According to the complaint, Williams then grabbed the boy and tried to slam him on his bed but missed.

Williams told police he brought the boy downstairs, and when he continued to be unresponsive, he and the boy's mother took JohnMarquis to the hospital Monday morning.

WPXI learned detectives gathered evidence at a home on Highland Avenue in North Braddock Monday as part of the investigation into what caused the boy's injuries.

Animal control was also called to the home.

WPXI also learned that Williams is a tier 3 sex offender, meaning he wasn't allowed to be around children. County police have yet to say whether Williams will face more charges in the case because of his sex-offender status.

"No child, regardless of the circumstances, deserves to be beaten that severely,” said Raymond Stepich, JohnMarquis’s uncle.

Stepich told WPXI on Friday that Williams' story doesn't match the severity of his nephew's injuries.

"He had bruises throughout his body, his arms (and) his chest. He had scratches on his neck (and) his head,” he said.

Stepich told WPXI that JohnMarquis' mother lost custody of her other two children, ages 4 and 13, on Friday. The children are now in the custody of their grandmother.

"We're just trying to make sure the kids are together, and they're in a safe place,” he said.

Stepich added that Allegheny County Children, Youth and Families had been to the home before, but nothing changed.

"Someone could have done something before it got to this point. That boy did not have to die for someone to step in and do something,” he said.

Family members have organized several benefit dinners and shows and started a GoFundMe page to pay for JohnMarquis’ funeral and burial. Anyone who wishes to donate can

.