An 11-year-old girl has officially been charged in the death of a toddler she was left alone to watch.

Her mother left the young girl and the 1-year-old boy at her home while she ran an errand, police in Maryland announced on Friday (March 1). The children’s families were were friends and the mother of Paxton Davis, the toddler, left him with the 11-year-old’s family on Saturday night.

Prince George’s County police say the next morning, the girl’s mother ran an errand and left the children alone at her Washington D.C.-area residence, according to the AP. When family members returned to the home the found Paxton injured and called 911. The young boy was taken to a hospital with severe injuries to his upper body and hospital staff contacted law enforcement.

Paxton would die on Thursday from the injuries he sustained. The young girl admitted to detectives that she assaulted the boy, according to Prince George’s County Police Maj. Brian Reilly. "It was an innocent, friendly agreement that obviously turned absolutely tragic," he said.

The girl’s name has not been released. She was reportedly charged with first-degree child abuse resulting in the death and committed to a juvenile facility. Even though they spoke to the girl at length, detectives still couldn’t establish a clear motive.

Maryland law states that a child cannot be left unattended without proper supervision by a reliable person that is at least 13 years old. Charges for the girl’s mother have not yet been announced as they are pending a consultation between police and the State’s Attorney’s Office.