Originally Published: 16 MAY 23 03:26 ET

Updated: 17 MAY 23 21:18 ET

By Steve Almasy and Elizabeth Wolfe, CNN

(CNN) — A 98-year-old woman and her 73-year-old daughter were among the three people killed by an 18-year-old high school student who roamed through his neighborhood Monday firing indiscriminately at homes and passersby in their vehicles, according to authorities in the northwestern New Mexico town of Farmington.

In all, Beau Wilson shot nine people Monday morning before four Farmington police officers fatally shot him, police officials said at a Tuesday news conference.

Gwendolyn Schofield, 98, and daughter Melody Ivie, 73, were killed in their vehicle and Shirley Voita, 79, who also was shot in a car, died at a hospital, according to authorities. Police had previously shared an incorrect spelling of Voita’s last name.

Farmington Police Sgt. Rachel Discenza was wounded in the exchange of fire with the assailant and New Mexico State Police officer Andreas Stamatiadas was shot as he came to the scene.

Four other wounded victims were hospitalized, but like the officers, have been released, Farmington Deputy Chief Baric Crum said.

“The amount of violence and brutality that these innocent people faced is something that is unconscionable to me. And I don’t care what age you are. I don’t care what else is going on in your life. To kill three innocent elderly women that were just absolutely in no position to defend themselves is always going to be a tragedy,” Farmington Deputy Chief Kyle Dowdy said Tuesday.

Investigators are still working on a motive for the shooting, Dowdy said. Interviews with Wilson’s family indicated they had concerns about his mental health, but it was unknown whether Wilson had been diagnosed with any mental health issues, he added.

The shooter only had “minor infractions” as a juvenile, so he was not on the radar of authorities, the deputy chief said.

The gunman turned 18 in October 2022 and the next month purchased one of the three weapons used in the shooting, Dowdy said. The deputy chief said police believe the other weapons were legally owned by a family member and they are investigating how the shooter got them.

One of the guns was an assault-style rifle – a weapon of choice among US mass shooters in recent, high-profile massacres, including the 2012 Sandy Hook school attack and a shooting in Uvalde, Texas, nearly a year ago that left 19 children and two teachers dead.

The attack left Farmington “shaken to the core by an unthinkable incldent that robbed families of their loved ones,” Mayor Nate Duckett told reporters. It is the latest American city to experience the wider scourge of US gun violence that’s resulted in 225 mass shootings in the first 20 weeks of the year.

The shooter walked through the neighborhood in this commercial hub near the Southwest’s Four Corners and “randomly fired at whatever entered his head to shoot at,” before police fatally shot him, Police Chief Steve Hebbe said in a video statement Monday night.

“There were no schools, no churches, no individuals targeted,” he said.

Dowdy said investigators have not seen a link between the assailant and the victims, but the shooter was staying at a residence in the neighborhood.

Investigators are piecing together how the attack that left more than 150 shell casings over a “wide and complex scene” that spans more than a quarter of a mile unfolded, authorities said. The assailant fired at three vehicles and six houses, though none of the victims was in a residence.

Dowdy said investigators were still at the scene and haven’t found all the shell casings it was unclear how many of those the gunman fired.

Discenza, a patrol sergeant with 10 years at the department, was wearing body armor but was hit by a bullet in the pelvic region, police officials said.

Stamatiadas was shot while driving to the scene, officials said, and drove himself to a medical facility, according to the chief. The mayor said both have been released from the hospital.

Five people were treated at the scene for injuries such as cuts from flying glass.

The shooting was first recorded on a doorbell camera at 10:56 a.m. MT and then emergency dispatch received “hundreds” of calls for an active shooter, police said. Officers were dispatched one minute later, including three who on their way to lunch and responded without body armor.

They arrived at 11:02 and four minutes later the officers killed the gunman, according to Dowdy. Farmington officers were the only law enforcement personnel who shot at the gunman, firing 16 rounds total, officials said.

Wilson was a student at Farmington High School, which was set to have its graduation ceremony Tuesday evening.

Authorities expect to hold another news conference Wednesday.