A man beat his girlfriend's 4-year-old son to death after she left the boy in his care while she was deployed to Iraq, police said.

Donell Parker, 23, was charged Friday with first-degree murder in the death of Cameron Smith. The boy was found dead in his bed Thursday in a suburb south of Chicago.

Parker told police he beat the boy, but would not say why, said Calumet City police Chief Patrick O'Meara.

Cameron was punched in the head, stomach and chest, and whipped with a belt from Tuesday to Wednesday evening, O'Meara said. An autopsy found he died of blunt-force trauma to the abdomen and head, O'Meara said.

The boy's 7-year-old sister and 8-year-old brother had also been in Parker's care, O'Meara said. They were put in the custody of their maternal grandparents after Cameron was found dead.

Cameron's mother, Sgt. Lavada Smith, 28, was headed back to Illinois Friday after spending only ten hours at her new duty station in Iraq.

She was called to active duty in April with her Army National Guard unit and was sent to Fort Benning, Ga., on May 12 in preparation for deployment, said Lt. Col. Alicia Tate-Nadeau, an Illinois National Guard spokeswoman.

Family members said Cameron's father, Gary Smith Jr., 27, had been deployed to Iraq last August and last saw his three children on a brief leave in January. O'Meara said the children's parents were separated.

Family members said the Smiths had been married for eight years, and had both been in the military most of that time. O'Meara said Lavada Smith had apparently been living with Parker for about a year.

Parker was scheduled to appear Saturday in bond court in suburban Markham, Ill. An official at the Cook County Circuit Court on Saturday could not immediately identify Parker's lawyer.