New York (CNN) An Indiana teenager pleaded guilty to killing a high school cheerleader who was pregnant with their child.

In a deal entered Wednesday, Aaron Trejo pleaded guilty to one count of murder and one count of feticide, both felonies. Last December he confessed to fatally stabbing his classmate, who was six months pregnant, in the heart and then concealing her body in a dumpster with a black plastic bag, according to court documents.

"I took action. ... I took her life" because it was too late for her to have an abortion, Trejo, 17, had said. According to court documents, Trejo said that neither he nor his victim, Breana Rouhselang, 17, wanted to have the child.

CNN was unable to reach Trejo's family. His attorney James Korpal declined to comment.

Trejo murdered Rouhselang using a knife because he thought it would kill her quickly, court documents show. After taking Rouhselang's life, Trejo threw the knife and her cell phone into a river. An autopsy confirms that her scarf was tied so tightly that strangulation occurred before she died from multiple stab wounds. Documents did not specify who tied the scarf.

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