A high school football player in Indiana was charged with murder on Monday after the authorities said he fatally stabbed a 17-year-old classmate who was six months pregnant with their child.
The football player, Aaron Trejo, 16, told the authorities that he had gotten into a fight with the girl, Breana Rouhselang, a former cheerleader, because she had waited too long to tell him about the pregnancy and it was too late to get an abortion.
“I took action,” Mr. Trejo said, according to the police. “I took her life.”
Mr. Trejo, who was charged as an adult, also faces one count of feticide. He was being held without bail at the St. Joseph County Jail.
The case has gripped Mishawaka, Ind., a city of about 50,000, and Mishawaka High School, where both students were in their junior year and where students walked out on Monday morning for a moment of silence to honor Ms. Rouhselang. She had played softball and served as a manager for the football team before she went missing over the weekend.
“These are the types of senseless tragedies that shake our small town community to its core,” Mayor Dave Wood of Mishawaka told WSBT, a local television station.
Ms. Rouhselang’s mother reported her missing at about 4:30 a.m. on Sunday. She said her daughter had left to talk to the father of her child hours earlier, but did not return home.
When the police questioned Mr. Trejo, he initially told them that he had gone to meet Ms. Rouhselang but that she did not show up, according to a probable-cause affidavit.
The authorities found glasses and a bloody hat that belonged to Ms. Rouhselang in the alley behind her home. Her body was found Sunday in a dumpster behind a nearby business, the affidavit said.
Eventually, Mr. Trejo confessed to the crime and was arrested on Sunday, according to the authorities.
He told the police that he had been thinking about killing Ms. Rouhselang and the baby for about a week, and had brought a knife and a black plastic bag on the night that he met up with her, according to the affidavit.
He stabbed her in the chest “because he thought it would kill Breana quickly,” the affidavit said. Mr. Trejo also confessed to putting a plastic bag over her and leaving her in the dumpster before going to the river to dispose of the knife and her cellphone, the authorities said.
An autopsy, which confirmed that Ms. Rouhselang was pregnant, showed that she had died from multiple stab wounds and was also strangled by a scarf around her neck, the affidavit said.
Court records did not list a lawyer for Mr. Trejo. Efforts to reach the families of Ms. Rouhselang and Mr. Trejo on Monday night were unsuccessful.
The Mishawaka High School football team had been scheduled to celebrate the season with an annual banquet on Sunday, according to WNDU 16, but postponed the party as it grappled with the news that one of its players had been arrested in the death of a team manager.
“The football team and all of the people that are associated with the football program obviously are grieving for the young lady — and they are also grieving for the young man because of his actions,” A. Dean Speicher, the superintendent for the Mishawaka school district, told the television station.
On Monday, during the moment of silence at Mishawaka High School, students wrapped their arms around each other.
“We’re in a period of grieving now,” Dr. Speicher said.