GILBERT, Ariz. - A Gilbert father faces a charge of felony child abuse after his 3-month-old son was taken to a hospital with serious internal and external injuries earlier this month.

Nathan Clapp, 36, stands accused of abusing the infant boy after a physician's review showed the boy's injuries were more severe than could have been caused by Clapp's description of his interaction with his son, according to police documents.

The boy was taken to Cardon Children's Hospital and diagnosed with 7 fractured ribs, lacerated liver, head bleed and fluid in his lungs on Aug. 12.

Clapp told police he may have rolled over on his son while he was napping while home alone with the boy after a long shift at work. He also said he tripped in his kitchen while holding the boy.

But police documents show a review from a doctor determined the injuries were significantly more severe than either explanation was likely to cause.

Additionally, police found text messages from Clapp to his girlfriend, the boy's mother, complaining about the boy's crying, saying he was "getting frustrated and this was the type of thing that makes a parent hurt their child," according to police documents.

After investigating, police arrested Clapp Tuesday morning.