A D.C. Superior Court judge sentenced a District man to 25 years in prison Friday for the beating death of his then-girlfriend’s 20-month-old son while he was babysitting the boy.

Judge William M. Jackson sentenced Jonathan Fullard, 29, in the killing of Keyontae Osbia Moore on March 4, 2012. Fullard was originally charged with first-degree murder. In October, he pleaded guilty to second-degree murder.

Fullard was watching the child while his then-girlfriend went to work. According to court documents, Fullard told police that he was “play boxing” with the boy about 12:30 a.m., striking him with closed fists to his body five or six times. He hit the boy in the head “by accident,” Fullard told police.

The medical examiner’s report said the child had bruises on his face, head, chest, back and left leg, three rib fractures, signs of sexual abuse and other injuries, according to court documents.