There was a tragic triple murder in a suburb of Chicago Sunday night that left dead an adult male, a teenage girl, and a 9-year-old girl.

The alleged killer in those slayings, 17-year-old Byrion Montgomery, pleaded not guilty in court on Tuesday to the numerous felony charges pressed against him, local ABC affiliate WLS reported.

Triple homicide leaves two young girls dead

Shortly after 8 pm Sunday, police in Bolingbrook, Illinois responded to reports of a possible home invasion in an otherwise quiet neighborhood and discovered upon their arrival at the scene that four people had been shot, only one of whom was still alive.

Two of the victims were identified as 40-year-old Cartez Daniels and his 9-year-old daughter Sanai Daniels, while the third victim was identified as 17-year-old Samiya Shelton-Thomas, who is believed to have been dating Montgomery.

The fourth victim who survived is believed to be Shelton-Thomas' 34-year-old mother, who was engaged to Daniels and was listed in critical but stable condition at a nearby hospital.

Police reported that two boys aged 14 and 3 had also been present in the home at the time of the shooting but were not injured.

Charged with multiple felonies, including first-degree murder

CBS News reported that Montgomery will be tried as an adult and has been charged with nine counts of first-degree murder -- three counts for each victim -- as well as a count each of attempted murder, aggravated battery, aggravated unlawful use of a weapon, and home invasion.

If convicted, he will likely spend the rest of his natural life behind bars in prison.

Montgomery is alleged to have shot all four victims and to have also stabbed Daniels to death. He was apprehended near his own home less than two hours after the incident and is currently being held by Will County authorities on a $20 million bond.

Police are still investigating the fatal shooting and no motive for the murders has been revealed as of yet.

Pleaded not guilty; more charges likely

The Daily Herald reported that a shackled Montgomery didn't say much during a court hearing on Tuesday other than to acknowledge that he understood the charges against him and that he would be tried as an adult and not as a juvenile.

His assigned public defender, Chris Benson, informed Judge Dave Carlson that Montgomery intended to plead not guilty to the charges, and a next court date of March 30 was set.

The outlet noted that Will County Assistant State's Attorney Peter Wilkes declined to discuss any of the details of the case against Montgomery with reporters as the police investigation of the "domestic-related home invasion" had not yet concluded and that it was "an ongoing process."

However, the prosecutor did reveal that the felony counts filed on Monday against the suspected killer were just initial charges and that he anticipated filing a broader "full set of the charges" against Montgomery prior to the March 30 hearing.

School district responds to murder of two students

The Herald further reported that the two slain girls were both students in the Valley View School District and that District Superintendent Rachel Kinder released a statement in regard to their untimely deaths.

"Two of the victims who lost their lives are Valley View School District students. The VVSD community is shocked and saddened by the loss of two of our students," Kinder said. "We have reached out to the families involved to express our condolences and to offer our support as they experience this devastating loss."

"In addition, we have initiated the District Crisis Response Plan to support our school communities and families that have been greatly impacted by this senseless act of violence," the superintendent added.