A fire captain in California, accused of murdering his girlfriend and her young son, and trying to kill another child, pleaded not guilty in court on Monday.

Darin McFarlin, a 47-year-old with CalFire, is currently on unpaid leave, according to KXTV. He was arrested last week following the deaths of 29-year-old Marissa Herzog (formerly known as Marissa Divodi-Lessa) and her son Josiah, who was in second grade.

He stands charged with two counts of first degree murder, one count of attempted murder, and domestic violence and child abuse charges.

According to court documents, the killings were meant to stop the victims from testifying in a separate crime, though the specific crime remains undisclosed. The documents outline what investigators believe transpired on the night of August 21.

The Sacramento Bee reports that prosecutors allege McFarlin assaulted Herzog in a bedroom before she left to make a phone call. He allegedly then obtained a gun and followed her to the dining room to commit the murder. The document describes Herzog’s death as “willful, deliberate, and premeditated,” asserting that she died because she was a witness to a crime, as noted by the Mountain Democrat.

The boy was also killed because he witnessed a crime, the newspaper said.

McFarlin is also accused of attempting to harm a second child, identified by Herzog’s family as her daughter. The court documents allege that he “willfully and unlawfully inflicted unjustifiable mental suffering” on the child in circumstances likely to cause significant harm.

When El Dorado County deputies arrived, Herzog was found deceased, according to CrimeOnline. The boy was transported to a hospital but later succumbed to his injuries. McFarlin fled the scene but was subsequently apprehended in Mono County, several counties away.

The El Dorado County District Attorney’s Office added special circumstances to the murder charges — committing multiple murders, murder of a witness to prevent testimony, and intentional discharge of a firearm causing death and child endangerment — making McFarlin eligible for the death penalty if he’s convicted, the Bee reported.

McFarlin is being held without bail and has a preliminary hearing set for September 29.