An Indiana judge on Tuesday entered a plea of not guilty for a high school football player who authorities say confessed to killing a cheerleader because she was pregnant with his baby and didn't tell him soon enough.

Aaron Trejo, 16, is being held at the St. Joseph County Jail without bail after the not guilty plea was entered for a count of murder and a count of feticide, according to NBC affiliate WNDU.

Trejo was arrested Sunday after Breana Rouhselang's mother reported her missing and investigators found her body covered in a black garbage bag and in a dumpster behind a Mishawaka restaurant, according to prosecutors.

Aaron Trejo

Charging documents filed Monday said that Trejo told a detective that Rouhselang, 17, had waited too long to tell him she was pregnant with his baby, preventing her from getting an abortion.

"I took action...I took her life," Trejo told the homicide detective, according to the documents. Rouhselang was six months pregnant, her stepmother told reporters Sunday.

Trejo said he killed Rouhselang with a knife "because he thought it would kill Breana quickly," the documents said. He said he had been planning the murder for about a week and brought the knife and a plastic bag from home to cover her body.

The teen said he threw the knife and Rouhselang's phone into a river after dumping her body in the dumpster.

Rouhselang died from multiple stab wounds, but a scarf was tied so tightly around her neck that she was being strangled before she died, according to an autopsy.

Investigators questioned Trejo after Rouhselang's mother told police that she last saw her daughter when the teen went outside to have a conversation with Trejo.

Trejo originally said he and Rouhselang had planned to meet, but she never showed. After an investigator asked if they had been fighting about the pregnancy, he confessed.

Officials said Monday that Trejo is a football player at Mishawaka High School and Rouhselang was a team manager, along with being a softball player and cheerleader.

Trejo is expected back in court on Dec. 19.