An Essex man who was caring for his girlfriend's 15-month-old baby was charged with first-degree murder Tuesday after the child died from what police called "severe internal injuries and heavy bruising from blunt-force trauma."

Brian Maurice Savage, 21, and the boy's mother were living together in an apartment in the 1400 block of Hadwick Drive, where the woman left the toddler in Savage's care on Sunday afternoon while she went to work, said Bill Toohey, a spokesman for the Baltimore County Police Department.

Two other people were in the apartment at the time, but police said Savage was the only person supervising the child, Cameron Justin Williams.

Savage told police he was in bed with the boy some seven hours after his mother's departure and noticed that he was unresponsive. Savage called 911 and Cameron was taken to Franklin Square Hospital Center in White Marsh, where he was pronounced dead.

Savage, who is 6 feet, 1 inch tall and weighs 185 pounds, said the injuries might have occurred while he was "roughhousing" with the toddler and rolled on top of him.

An autopsy on Monday determined that the toddler's internal injuries included damage to his lung, liver and spleen, as well as bruises and cuts on his head and body.