A 12-year-old boy in Fort Washington has been charged with second-degree murder in the beating death of a 2-year-old girl who was staying with his family as a foster child under the supervision of social services officials, Prince George’s County police said.

The victim, Aniyah Batchelor, had been in foster care since November, according to her mother, Stephany Cunningham, who has two other children, both being cared for by other people. Aniyah, who turned 2 in March, had been placed with a family of five in a house in the 1800 block of Taylor Street, where she was beaten by the 12-year-old boy Tuesday, police spokeswoman Julie Parker said.

Parker would not say whether detectives had determined a motive for the attack, but she said the 12-year-old boy had “beaten the child repeatedly” in a single incident. No weapon was used, she said.

The foster parents, a man and a woman, were not at home at the time of the incident, Parker said. She said the parents have three biological children — girls ages 15 and 4, in addition to the 12-year-old boy — and that the older girl was in charge of the other youngsters when the beating occurred.

Without providing a specific timeline of events, Parker said the foster father “was summoned home” late Tuesday morning, after the beating, and found Aniyah unconscious. He called 911 at 12:09 p.m. As an ambulance headed to the house — a neatly kept brick-front split-level with red shutters and a small front lawn — the father tried to revive Aniyah with cardiopulmonary resuscitation, Parker said.

The girl was pronounced dead at a hospital. After an autopsy Wednesday, Parker said, the Maryland medical examiner’s office concluded that the girl was a homicide victim and that the cause of death was blunt-force trauma. Shortly afterward, the boy was charged with second-degree murder.

Second-degree murder, or murder that is not premeditated, is a lesser crime than first-degree murder. Because the boy was charged as a juvenile, police declined to identify him, who they said is being held at the Cheltenham Youth Facility.

Cunningham, 25, of Landover said her other children are a 5-year-old girl and a 3-year-old boy. Last fall, she said, she had custody of Aniyah and her other daughter, but her son was being cared for by a relative. Cunningham said she was living in an Adelphi apartment at the time. One day in November, she said, the relative brought the 3-year-old boy to visit her, and a horrible accident occurred.

Cunningham said someone — not her — mistakenly put the boy in a tub filled with scalding water while trying to give him a bath. “He got all burned,” she recalled, sobbing loudly on the phone. “His skin was coming off real bad.”

As a result of that incident, Cunningham said, a Prince George’s County judge removed the two girls from her custody. She said that the 5-year-old girl went to live with a foster family in the District and that Aniyah was placed with the family in Fort Washington.

Foster children in Prince George’s are the responsibility of the county’s Department of Social Services and its parent agency, the Maryland Department of Human Resources. Police referred all questions about the Fort Washington family to Pat Hines, a spokesman for the state human resources agency. Citing privacy rules, Hines would not discuss Aniyah or the foster parents’ history of caring for children under state supervision.

Cunningham said she usually visited with Aniyah on Thursdays at a county social services office. Over the months, she said, she got to know the foster parents, and she thought well of them until this week. “I want to know how can they let kids watch kids and let my baby get beat,” she said, crying on the phone.

Meanwhile, on Taylor Street, a woman named Jean Price spoke through tears about the 12-year-old boy, who was a neighbor. She said he would routinely stop playing basketball in his driveway to help her take groceries out of her car.

“I loved him so much,” she said. “He was the sweetest child you’d ever want to know.”

She said she and her husband, Jim Price, have known the family for about eight years, and she described the parents and youngsters as “wonderful.”

“Their whole family is so special,” Jean Price said, adding that the 12-year-old boy sometimes talked with her about his grades. When she asked him what he wanted to be when he grew up, she said, he replied, “I want to be successful.”

“I told him you’re already on your way because you have the character that stands out.”

Police said the boy is the first preteen accused of murder in the county since 2006, when a 12-year-old boy was charged as a juvenile with stabbing and beating to death his mother and 9-year-old brother. Prosecutors later said that the boy, who did not have a previous arrest record, pleaded “involved” — the equivalent of guilty — in juvenile court.

Under Maryland law, youths ages 14 to 17 can be charged with certain crimes as adults at the discretion of prosecutors, and upon conviction those teenager can be sentenced to an adult prison. In such a case, the burden is on the teenager to convince a judge in adult court that the matter should be handled in juvenile court.

After a juvenile court trial or plea, even a teenager who has committed a murder cannot be held in a detention facility beyond his or her 21st birthday.

With suspects younger than 14, like the Fort Washington youth, the case must start in juvenile court. In most instances, if prosecutors want the case moved to adult court, they must convince a juvenile court judge that the youngster’s criminal history is so heinous and extensive that rehabilitation in the juvenile system is not an option.

Although police would not discuss any criminal record involving the 12-year-old boy, Capt. Joseph R. Hoffman said police had not been summoned before to the house and had no history of involvement with the family.

Asked whether authorities would seek to have the case moved to adult court, Parker said police and prosecutors are conferring on that question. “At this point, he has been charged as a juvenile,” she said, but “that could change.”

Jennifer Jenkins contributed to this report.