OMAHA, Neb. (AP) — An Omaha man has been sentenced to prison in the death of his girlfriend’s 16-month-old son.

A judge on Tuesday sentenced 25-year-old Tyler Kennedy to 18 to 20 years in prison after he pleaded no contest in January to negligent child abuse resulting in death.

The Omaha World-Herald reports Kennedy has admitted that he slapped and shook the toddler while he was watching him on July 26, 2014. He first told police that the child choked on a bottle cap.

Kennedy apologized in court Tuesday and said he would mourn the loss of the boy.

He was not the child’s biological father but lived with the infant and his mother, Cindy Cooper.