FAIRBANKS -- Charges against a Fairbanks man accused in the death of his girlfriend's 2-year-old son have been upgraded from assault to first-degree murder.

Twenty-four-year-old Carl Delbert David is accused of throwing the boy and stepping on him because the child wet his bed.

The charge was upgraded Friday afternoon, the Fairbanks Daily News-Miner reports.

The criminal complaint says the boy suffered a fractured skull, a broken neck and other injuries.

David is being held at Fairbanks Correctional Center without bail.