MERCED — After a months-long manhunt, police arrested a suspect in the death of an 8-year-old girl who had been reported missing before her body was found last March inside a home, authorities said Sunday.

Dhante Jackson was taken into custody Saturday in Newark on suspicion of killing Sophia Mason, police and the California attorney general’s office said.

Investigators determined the child suffered continuous physical abuse, was malnourished and at times was forced to live in a shed in the backyard of Jackson’s home, Merced Police Department Lt. Joe Perez said during a news conference Sunday.

Jackson was in a relationship with the young victim’s mother, 30-year-old Samantha Johnson, who was arrested in March and has pleaded not guilty to murder and child abuse, prosecutors said.

Jackson, 34, also faces murder and child abuse charges. It wasn’t known Sunday if he has an attorney who could speak on his behalf.

Four other people were arrested Saturday on suspicion of helping Jackson evade arrest, Perez said.

“In my 20 years of law enforcement, this case is the most disturbing and horrific that I’ve seen,” the lieutenant said.

Relatives Reported the Child Missing

Sophia was reported missing by relatives in Hayward. They told police they had not had contact with the girl since December, and that she was known to stay at different locations between Hayward and Southern California.

The missing person report led Hayward police to arrest Johnson on a warrant stemming from a case of child abuse in Alameda County last year, police said.

Statements Johnson made to Hayward police prompted them to ask for assistance from the Merced Police Department, which served a search warrant in March at the house in Merced where Jackson lived, they said.

Merced police found Sophia’s body in a bathtub, inside a locked bathroom, according to court documents.

Mom Said Boyfriend Sexually Abused Child

Johnson told a Merced police detective that Jackson, her boyfriend, had kept Sophia in a shed and that the child was subjected to physical and sexual abuse by Jackson.

Sophia twice personally told social workers that her mother had choked and hit her, according to child-welfare documents uncovered by the Bay Area News Group.

At one point, the internal documents show, a teacher and a social worker reported grave concerns over what they considered signs of abuse.

Sophia’s grandmother, Sylvia Johnson, last week filed a wrongful death legal claim against Alameda County, alleging the Department of Child and Family Services didn’t do enough to protect the little girl.

Alameda County has 45 days to respond to the family’s claims, the news group reported Sunday. If no settlement is offered by the county and the claim is rejected, the family has six months to file a lawsuit.