Sixteen-year-old Aaron Trejo has been formally charged with murder and feticide in the death of pregnant 17-year-old Mishawaka High School student Breana Rouhselang.

Her body was pulled Sunday from a dumpster behind Pasquale Rulli's Restaurant in Mishawaka.

Trejo, a Mishawaka High School football player, was taken into custody and was held on a preliminary murder charge.

On Monday, he was formally charged as an adult with murder and feticide, two felonies.

Charging documents included the following account from Detective Gery Mullins:

After a brief break, I, Detective Mullins, began to ask pointed questions of Aaron and confronted him with the fact that the physical evidence was not going to support his story and that I suspected Aaron knew more than he was telling. There were several pauses and quiet times. I then asked Aaron if the fight was about the pregnancy. Aaron Trejo quietly said, "Yes." Aaron then explained that Breana waited too long to tell Aaron about the pregnancy to get an abortion. I asked Aaron what he did about that, and he replied, "I took action...I took her life." Aaron explained that he stabbed Breana in the heart with a knife he brought from home. Aaron chose to use a knife because he thought it would kill Breana quickly. Aaron stated that he put the black plastic bag over Breana, which he had brought from home for that purpose. Aaron Trejo said that he had been planning and thinking about killing Breana and the baby for about a week and had not told anybody. Aaron Trejo said that after he put Breana's body in the dumpster, he walked to the river and threw Breana's phone and his knife as far out into the river as he could. An autopsy confirmed that Breana Rouhselang died from multiple stab wounds, that her scarf had been tied so tightly that strangulation was occurring before Breana died, and that she was pregnant. The manner of Breana Rouhselang's death is homicide.

Trejo was arraigned Tuesday afternoon, and the judge entered a preliminary "not guilty" plea. Bail was denied because of the murder charge.

He'll be back in court on Dec. 19.

Rouhselang was a cheerleader and softball player at Mishawaka High School. Her family reported her missing just hours before her body was discovered.

When police arrived at the 400 block of Battell Street around 4:30 a.m. Sunday, they found evidence of a violent crime before ultimately discovering Rouhselang's body in the dumpster.

The victim's stepmother told NewsCenter 16 that Rouhselang was 6 months pregnant.