(AP) — Police have charged a Mississippi mother and her boyfriend after the woman’s 4-year-old daughter died and her 3-year-old daughter was hospitalized with injuries.

Natchez Police Chief Walter Armstrong said at a news conference Friday that the children suffered “severe beatings.”

He said 25-year-old Lakeisha Marie Jones of Natchez left her children with 24-year-old James Christopher Anderson while she worked Tuesday night.

After the girls were beaten, Anderson took them on a quarter-mile walk to an apartment complex where his mother lives, and one of the girls kept falling during the walk from being injured so badly, a police report said.

Armani Hill died Wednesday at a hospital in Natchez, and her 3-year-old sister is hospitalized in Jackson. The younger girl’s name has not been released.

Adams County Coroner James Lee said an autopsy showed Armani died from blunt force trauma.

“I wish I had the correct words to describe how devastating this is,” Lee said. “God have mercy.”

Anderson is charged with two felony counts of child abuse.

Jones is charged with two counts of child deprivation of necessities with substantial harm. Investigators said she knew Anderson was abusing her children and failed to stop him.

Anderson and Jones remained jailed Friday. Police did not say whether either is represented by an attorney.

Armstrong said this is the worst case of child abuse he has ever seen. State social workers had twice previously investigated the family because of injuries to the children, he said.

“There’s indication that the abuse of these young babies had gone on for quite some time,” Armstrong said.