Breana Rouhselang was six-months pregnant and the suspect in her killing was the father, police allege

The Indiana high school football player accused of killing a cheerleader he had impregnated allegedly told police he planned the attack for about a week, according to an arrest affidavit obtained by PEOPLE.

Aaron Trejo, 16, is charged by St. Joseph County authorities as an adult with murder and feticide in the death of 17-year-old Breana Rouhselang — who was six months pregnant — and the unborn child she was carrying. Breana was a cheerleader at Mishawaka High School and a manager for the school’s football team on which Trejo played, her family told Fox59.

Police allege Trejo confessed to them in an interview after Breana’s body was found in a dumpster near her home last Sunday morning. During his confession, he allegedly said he met with Breana on Saturday night and stabbed her in the heart with a knife from home, and that he’d chosen the knife because he thought it would kill her quickly, the affidavit alleges.

When Breana’s body was found, a black plastic garbage bag had been placed over her head and upper torso. The affidavit alleges Trejo confessed he’d put the plastic bag on Breana and that “he had brought [the bag] from home for that purpose.”

Aaron Trejo
| Credit: St. Joseph County Prosecutor's Office

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Trejo was questioned after Breana’s mother told police her daughter was home Saturday night but left the house at 11 p.m. to talk to Trejo but never returned. Trejo initially told police that Breana did not show up to their planned meeting, but he later confessed they got into a fight about her pregnancy and that he killed her, the affidavit alleges.

Breana Rouhselang
| Credit: GoFundMe

The affidavit adds, “Trejo said that he had been planning and thinking about killing Breana and the baby for about a week and had not told anybody.”

It alleges that Trejo told police Breana had waited too long to tell him that she was pregnant so an abortion was no longer possible. “I took action, I took her life,” he then told police, the affidavit alleges.

Breana’s stepmother Nicole Rouselang wrote on a GoFundMe page created in her honor, “This is such a hard tragedy to accept! This loving young lady was so full of life and didn’t deserve this.”

The page adds, “Please keep this family in your thoughts and prayers. No one can ever be prepared for a loss like this.”

The South Bend Tribune reports that on Monday, in honor of Breana, about 200 students at the school walked out of class and gathered at the school’s flag pole in silence.

It was not immediately clear if Trejo has an attorney. He will be arraigned on Tuesday afternoon, the Tribune reports.