Dante Jackson was taken into custody Saturday in the San Francisco Bay Area city of Newark on suspicion of murdering Sophia Mason, police and the California attorney general’s office said. Investigators found the child suffered constant physical abuse, was malnourished and was sometimes forced to live in a shed in the backyard of Jackson’s home, Merced Police Lt. Joe Perez said during a news conference Sunday. Jackson was in a relationship with the young victim’s mother, Samantha Johnson, 30, who was arrested in March and has pleaded not guilty to murder and child abuse, prosecutors said. Jackson, 34, also faces charges of murder and child abuse. It was not 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 20 years of law enforcement, this case is the most disturbing and gruesome I have seen,” said the lieutenant. Sophia was reported missing by relatives in the San Francisco Bay Area town of Hayward. They told police they had not had contact with the girl since December and that she was known to live in different locations between Hayward and Southern California. The missing person’s report led Hayward police to arrest Johnson on a warrant stemming from a child abuse case in Alameda County last year, police said. Statements Johnson made to Hayward police prompted them to seek help from the Merced Police Department, which served a search warrant in March at the Merced home where Jackson lived, they said. Merced police found Sophia’s body in a bathtub inside a locked bathroom, according to court documents. Johnson told a Merced police detective that Jackson, her boyfriend, had kept Sophia in a shed and that the child had been physically and sexually abused by Jackson. Sophia twice told social workers in person that her mother had choked and beaten her, according to child welfare documents disclosed by the Bay Area News Group. At one point, internal documents show, a teacher and a social worker raised serious concerns about what they considered signs of abuse. Sophia’s grandmother, Sylvia Johnson, filed a wrongful-death lawsuit last week against Alameda County, alleging that the Department of Children and Family Services did not do enough to protect the little girl. Alameda County has 45 days to respond to the family’s allegations, the news group reported Sunday. If no settlement is offered by the county and the claim is denied, the family has six months to file a lawsuit.