MANHATTAN, Kan. (AP) — A Manhattan man has been sentenced to life in prison for killing his ex-girlfriend’s baby.

Andrew Gibson, 28,  must serve 25 years of his sentence for first-degree murder in the May 2016 death of 3-month-old Serenity Reich before becoming eligible for parole. He also was sentenced Thursday to three years for child abuse.

Gibson previously dated Serenity’s mother, Ariel Reich-Wille. While she was out of town, Gibson volunteered to watch her two children, including Serenity, at his apartment.

While being interrogated, Gibson told investigators he pushed the infant’s face into a mattress top. A medical examiner determined Serenity died from asphyxiation. The medical examiner also found bruises on the baby’s scalp and upper back, as well as multiple rib fractures that had started to heal.