A Somerset man assaulted an 11-day-old infant and fractured the baby's arm, leg, skull and nose during an altercation with the child's grandmother, police said.

Jeremy Smith, 31, has been in Somerset County Jail since Jan. 1 for allegedly assaulting the woman, but the infant's injuries were unknown until Wednesday when it was treated in Pittsburgh's Children Hospital for an unrelated medical problem, police said.

Police accuse Smith of injuring the baby by assaulting the grandmother while she was holding the infant.