Aaron Romeo Trejo, 18, of Mishawaka, Ind., was sentenced Tuesday to 65 years in prison for felony murder and feticide for murdering a teen who was pregnant with his child. He was 16 years old when he stabbed 17-year-old Breana Rouhselang in the heart and placed her body in a dumpster behind a pizzeria in December 2018, according to a probable cause affidavit.

Trejo had been ruminating for a week about killing Rouhselang, a multisport athlete who played softball and managed the football team, the affidavit stated.

Rouhselang was a lifelong athlete and wanted to study athletic training when she graduated from high school, according to her obituary.

She had waited too long to tell him about the pregnancy, and neither of them wanted the baby, Trejo told authorities. She was six months pregnant when she died, according to her obituary.

Indiana doesn't allow abortions after 22 weeks, according to the Kaiser Family Foundation.

Rouhselang's mother, Melissa Wallace, knew her daughter had gone to an alley behind the house to speak with Trejo about 11 p.m. on a Saturday, according to court documents.

Wallace and Rouhselang's father, Dave Rouhselang, didn't respond to requests for comment.

Wallace told police that she woke up about two hours later, and that her daughter was missing. She went to Trejo's house, where he told her that Rouhselang never showed up to their scheduled meeting. He also told Wallace that he had lost his phone, so she wouldn't be able to reach him, police documents say.

In the place the teens were supposed to meet, police found glasses, a stocking cap and a bloody hat - items that matched what Rouhselang was last reported wearing, according to court records. More blood was sighted before Rouhselang's body was discovered with a black plastic garbage bag covering her head and upper torso, according to the affidavit.

Trejo and his parents were taken to a homicide unit where Trejo recounted the same story he had given to Rouhselang's mother and police. He ultimately admitted the truth under questioning.

"I took action. . . . I took her life," he told the detective, before confessing that he threw his knife and Rouhselang's phone into a river.

An autopsy found that Rouhselang died of multiple stab wounds and suffered from strangulation before her death, according to the affidavit.

Trejo entered a not-guilty plea days after he was booked. He changed his plea to guilty in October, court records show.

The St. Joseph County superior court judge who sentenced Trejo on Tuesday ordered a DNA sample from him but didn't specify why.

Trejo's attorney and sister didn't immediately respond to requests for comment.

It's unclear whether Trejo and Rouhselang, who had known each other since elementary school, had an ongoing romantic relationship or a history of violence.

An April 2019 study in the Journal of the American Medical Association Pediatrics found that adolescent girls were 90% of victims killed by current or former intimate partners. The average age of the victim was about 17 years old.