Utah judge advances manslaughter case against No Kings volunteer who thought he was preventing a mass shooting

A Utah judge ruled Tuesday there is probable cause to try Matthew Alder on manslaughter charges after he fired three rounds at Arturo Gamboa, a man in black with a rifle at a June 2025 No Kings protest in Salt Lake City. One shot hit Gamboa; another killed protester Arthur Ah Loo, who was standing between Alder and his target.

Alder told police he feared Gamboa was about to 'mag dump' into the crowd; his attorneys argued the fatal shot may have ricocheted, which a detective disputed on the stand. Prosecutor Josh Graves countered that every pull of the trigger was a conscious choice made in the direction of a crowd.

Safety team witnesses described a tense day shadowed by armed counterprotesters and the same-morning assassination of two Minnesota lawmakers; one unarmed volunteer who spotted Gamboa assembling the rifle called it 'beyond suspicion.' Gamboa, who fled and discarded his gear before being identified by protesters, says he was asserting his First and Second Amendment rights. Police never found evidence the rifle was loaded.

The full dispatch is available from the source below.