A 27-year-old West Virginia man has been charged with murder after he admitted to throwing his 1-year-old stepson on Sunday when he was fussy and wouldn’t lay down for a nap.

The boy suffered a skull fracture and died at a hospital about an hour after emergency crews were called, WDTV reported.

Zachary Williams, 27 was charged with first degree murder.

Police spoke with the baby’s grandparents, who lived with Williams and the child’s mother, who told them that the boy had been fine that morning except for suffering from a cold.

Investigators were told that the boy bumped his head while crawling on the floor that morning, leaving a “little red mark.” He had a bruise over his left eye, but an autopsy uncovered a severe skull fracture on the back of the baby’s head.

The baby’s mother told the medical examiner that the child had been fussy because of his cold, and that she fed him breakfast Sunday morning before the grandparents left the house. Then she decided to put him down for a nap.

When the boy fought sleep more than usual, she woke up Williams for some help, the criminal complain says. He took the baby into the bedroom and soon began calling for the mother, who found her son limp. She called 911 and started CPR.

Williams told police he was bouncing the boy to try to soothe him, but that he suddenly went “rigid and limp” and became unresponsive.

After the autopsy, Williams admitted that he threw the baby out of frustration, slamming his head on the bed frame and the floor. He told investigators at that point that “it was all his fault.”

Williams was ordered held without bond.