A 14-year-old fatally shot a 13-year-old girl. Now his father is on trial.

The trial began this week against William Brown, 39, the father of the 14-year-old boy who fatally shot a 13-year-old girl nearly a year ago.

Brown is the first person to be charged under the Bennie Hargrove Gun Safety Act, aka "Bennie's Law," a New Mexico law that allows adults to be held criminally liable for negligently allowing a minor to access a firearm. A jury was seated Monday night.

Brown's son is accused of killing the 13-year-old while hanging out with friends at his home in Questa in July 2023. The 14-year-old shot the girl in the face while playing with a gun that belonged to his father, according to police. He then "dragged the female's body outside and returned to the residence," police said.

Police said Brown arrived at the home shortly after the shooting, and "when officers arrived, the juvenile and Brown refused to come out of the residence for approximately 30 minutes."

The teen was tried for second-degree murder, as well as tampering with evidence and assaulting a police officer, but the case ended with a hung jury in March. He is expected to go on trial again in August.

On Monday, the trial against the boy's father began, with prosecutors alleging his negligence in storing his firearms allowed the deadly shooting to occur.

Brown is facing fourth-degree felony charges. If convicted, he could face up to 18 months in prison.

"This being the first trial of the first parent being charged underneath [Bennie's] bill, there's a lot of eyes on this trial to see what happens. And not only that, but what's going to be happening afterwards," Shane Maier, an attorney for the victim's family, told Albuquerque, New Mexico, ABC affiliate KOAT.

Maier said the case against Brown will be pivotal for the enforcement of crimes prosecuted under Bennie's Law.

"The whole purpose of this law is to make sure parents understand that they can face consequences for allowing kids to have access to their firearms," Maier said. "There's some concerns that if it's not successful in the first couple trials or if it goes to the appellate courts, then they're going to come back and look at revising that law."

Bennie's Law was passed as a result of the death of 13-year-old Bennie Hargrove, who was shot and killed at his Albuquerque middle school in 2021.

New Mexico Gov. Michelle Lujan Grisham signed the bill into law in March 2023.

"Today, New Mexico is making it clear that responsible gun ownership is the law of the land," Lujan Grisham said at the time. "This bill is about keeping New Mexicans safe by requiring gun owners to take reasonable steps to secure their weapons – plain and simple."

The Hargrove family had been vocal supporters of the legislation, with the boy's grandmother, Vanessa Sawyer, saying she was "proud and grateful" after it was passed.

"It means a lot to our family," Sawyer said. "This bill's purpose follows Bennie's spirit in trying to protect young children and to save lives."