Two armed safety volunteers told investigators they saw Arturo Gamboa carrying a rifle and moving toward a crowd of demonstrators during the June “No Kings” gathering in Salt Lake City.
Only one of the men — Matthew Scott Alder — fired his weapon, and he killed protester Arthur “Afa” Folasa Ah Loo, prosecutors say.
Alder was charged Wednesday with one count of manslaughter, and if he is convicted, he could spend up to 15 years in prison. Court documents outlined new details in the June 14 shooting, including Alder’s statement to police that as he pulled out his handgun, he thought to himself, “Oh my God, this is happening, this is really bad, somebody’s going to get hurt.”
[Read more: Salt Lake County D.A. files charge in SLC ‘No Kings’ shooting nearly 6 months after protest.]
Alder fired three times, prosecutors say. One round struck 24-year-old Gamboa, wounding him, and another fatally struck 39-year-old Ah Loo, who was participating in the march. Thousands of protesters fled.
The second armed safety team member told investigators he believed Gamboa “was about to commit a mass shooting” and felt he “should have dropped him,” but added that he realized he didn’t have a clear shot.
“There’s no way I can shoot him when he’s running toward a crowd,” the safety volunteer, identified only as A.F. in the charging document, said. “I mean, I’m accountable for every bullet that comes out of my gun.”
Salt Lake County District Attorney Sim Gill said his office would not pursue charges against Gamboa because he was legally allowed to carry the rifle.
‘Gun, gun, gun’
(Francisco Kjolseth | The Salt Lake Tribune) Thousands who gathered for the "No Kings" protest scatter off State Street in downtown Salt Lake City following gun shots on Saturday, June 14, 2025.
The event’s volunteer safety team was intended to provide medical care, crowd management and de-escalation, investigators said in court documents. Some members of the team carried firearms, investigators said, but “there did not appear to be any formal training” for participants.
Alder told police that A.F. waved him over when he saw Gamboa in “complete black gear” with an assault-style rifle in a low position. A.F. said he knew open carry was legal, but became concerned because Gamboa was putting his rifle together while behind a building column, charging documents said.
Alder added that Gamboa was hunched down in what he believed to be “combat mode,” and that Gamboa appeared to be “charging the handle” of the gun to make it ready to fire.
A.F. said he called out “gun, gun, gun” over his radio to other organizers.
Confronting Gamboa
(Francisco Kjolseth | The Salt Lake Tribune) Police search for a suspected shooter during a "No Kings" demonstration in downtown Salt Lake City on Saturday, June 14, 2025.
A.F. and Alder said they both began yelling at Gamboa to drop the gun but Gamboa did not respond.
That’s when Alder allegedly first fired his weapon.
After this shot, Alder told investigators that Gamboa continued to move toward the crowd, and that he yelled at Gamboa to get on the ground. When Gamboa turned his head toward Alder with his rifle “still moving up from the lower position,” Alder fired two more shots at him, Alder told investigators.
Alder told authorities that at the time of the shooting, he was thinking “please God, don’t let me have to fire but I want people to be as safe as I can.” He added that he believed Gamboa was going to “mag dump into a crowd of people to kill as many people as he could,” and that Gamboa’s behavior “scared the hell out of me,” according to the charging documents.
Seconds after the shots were fired, video surveillance showed Gamboa running from the scene. Detectives believe the video shows that Gamboa did not have a magazine inserted into his rifle at that moment. However, investigators found three loaded rifle magazines in Gamboa’s cargo pants along with a knife, according to court records.
Alder told police he “fired a couple of shots towards the building to ward him off and get him to stop” but that Gamboa took off, according to police body camera footage cited in the charging documents.
“I can’t believe it, I saw him, he was loading an AR right there,” he later said in the same interaction. “I can’t believe it. I pulled behind the column, and I took shots at him.”