(CNN) An Indiana teenager who said he killed a pregnant schoolmate because she waited too long to tell him about her pregnancy has been sentenced to 65 years in prison, according to authorities.

Aaron Trejo was sentenced Tuesday in St. Joseph County Superior Court for the December 2018 killing of 17-year-old Brena Rouhselang. He had pleaded guilty late last year to murder and feticide.

The killing happened after Rouhselang, a cheerleader and junior at Mishawaka High School, told Trejo that she was six months pregnant, authorities said.

Trejo, then 16 and a member of the school's football team, was alleged to be the father, and neither of them wanted to have the child, according to court documents.

He confessed in December 2018 to stabbing Rouhselang and wrapping her in a plastic bag, having planned to kill her and the baby for about a week, court documents say.

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