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Flathead County Sheriff’s Office deputy spoke with suspect moments before fatal hit-and-run, according to court documents

JACK UNDERHILL | Hagadone News Network | UPDATED 1 year, 1 month AGO
by JACK UNDERHILL
KALISPELL GOVERNMENT, HOUSING AND TRANSPORTATION REPORTER Jack Underhill covers Kalispell city government, housing and transportation for the Daily Inter Lake. His reporting focuses on how local policy decisions affect residents and the rapidly growing Flathead Valley. Underhill has reported on housing challenges, infrastructure issues and regional service providers across Montana. His work also includes accountability reporting on complex community issues and public institutions. Originally from Massachusetts, Underhill graduated from the University of Massachusetts, Amherst with a degree in Journalism before joining the Inter Lake. In his free time, Underhill enjoys mountain biking around the valley, skiing up on Big Mountain or exploring Glacier National Park. IMPACT: Jack’s work helps residents understand how growth, housing and infrastructure decisions affect the future of their community. | August 25, 2025 12:30 PM

A Flathead County Sheriff’s Office deputy spoke with Jefferey Scott Serio just before he allegedly ran a pedestrian down with his vehicle, according to court documents.

Authorities are holding Serio, 48, on a pending deliberate homicide charge after he allegedly struck and killed a pedestrian in the Helena Flats area on Tuesday, Aug. 19. He remains in the county jail held on $500,000 bail. 

The victim, identified as Raymond Maurice Grigg, was found trapped underneath Serio’s abandoned vehicle and died at the scene.  

Law enforcement received a call around 7:38 p.m. on Aug. 19 about a suspicious male on a property on Grigg Road near Glacier Park International Airport, according to documents filed in Flathead County District Court.  

Serio told the deputy that his vehicle was parked at a neighboring property. The deputy told Serio to leave and stay off the property. Serio left on foot toward his parked vehicle, according to court documents.  

While leaving the area, the deputy heard an engine accelerate rapidly and what sounded like a vehicle driving through a cornfield, according to court documents. The deputy reported seeing the vehicle at the opposite end of the cornfield drive through a barbed wire fence before losing sight of the vehicle as it headed toward a property on Grigg Road, according to documents.  

The deputy heard gunshots and other law enforcement officers responded.

A witness, who lives on the Grigg property, told law enforcement that Serio was driving toward her house when she heard his vehicle hit something and heard gunshots as well, according to court documents. 

Another witness reported seeing Serio's vehicle burst out of the cornfield and through two fences, seemingly heading back to U.S. 2 before veering toward a nearby cell phone tower. The witness said he heard Serio’s vehicle crash and possibly reverse before revving the engine again. He also heard gunshots and a subsequent crash, according to court documents. 



Serio allegedly got out of his vehicle following the crash and was heard saying, “I tried to miss him,” before running down the road. 

Grigg was found pinned beneath the vehicle and deputies employed jacks to free him, officials said. Despite life-saving measures, including CPR, the victim died at the scene. The fatal collision occurred near the 100 block of Birch Grove Road north of Kalispell.  

Law enforcement reported finding five shell casings at the scene, with two bullet holes in the front of Serio’s vehicle.  

After arresting Serio, deputies took him to the county jail. 

Reporter Jack Underhill can be reached at 758-4407 and [email protected].

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