A firefighter from California faces murder, attempted murder and child abuse charges in the deaths of his 29-year-old girlfriend and her son.

Darin McFarlin, 47, stands accused of killing his girlfriend Marissa N. Divodi-Lessa and her son, who was identified by family as Josiah Divodi-Lessa. Divodi-Lessa is identified in the complaint as Marissa Herzog.

McFarlin is charged with two counts of murder and one count each of attempted murder, child abuse and domestic violence. According to prosecutors, McFarlin shot Divodi-Lessa in the dining room of their home as she tried to use a cellphone. He also allegedly tried to kill another child who was in the home at the time.

The complaint sheds light on a potential motive. Prosecutors allege that the two were killed “to prevent testimony.” The victims were witnesses “to a crime” and were “intentionally killed because of that fact.” It does not expand on what crime they had witnessed. Prosecutors with the El Dorado County District Attorney’s Office told Law&Crime that they could not comment beyond what is in the criminal complaint.

As Law&Crime previously reported, the El Dorado County Sheriff’s Office said its deputies responded to a shooting around 9 p.m. Thursday to a home in the 3000 block of Oakwood Road in Cameron Park, which is some 30 miles east of Sacramento. When they arrived, they found the two victims inside the home suffering from gunshot wounds. Divodi-Lessa was pronounced dead at the scene while paramedics rushed her son to the hospital, where he later died.

Investigators identified McFarlin as a person of interest and arrested him a few hours later on homicide charges. McFarlin works for California Department of Forestry and Fire Protection, known as CalFire.

According to local NBC affiliate KCRA, McFarlin is a fire captain for the Amador El Dorado unit. The agency, which is tasked with fighting California’s wildfires, told KCRA that it is monitoring the situation. Meanwhile, more than 1,000 of his fellow firefighters were battling a nearby wildfire at the time.

Divodi-Lessa leaves behind a daughter. A GoFundMe page included a message from the girl about her mother and younger brother, who went by JoJo.

She always made me laugh. She would always tuck [me] in at night and we would always tell each other, “I love you.” “I love you more.” “I love you most.” We loved playing card games, watching movies and hanging out. My brother, JoJo, would always play games with me, especially Hide-and-Seek. That day, we made a box with cute necklaces. The box had a lock on it. It was filled with toys in it (as rewards) for whenever he was good. He was such a sweet boy. JoJo had some health issues and Mommy was so good about being sure he had the right foods and proper care. She was the best Mommy everrrrr!

Josiah was a second grader at Blue Oak Elementary School, KCRA reported.

McFarlin remains at the El Dorado County Jail without bond.