File on GCSO deadly force incident goes to prosecutor

MOSES LAKE — An investigation has been completed by area law enforcement into the fatal shooting of a Moses Lake-area man by Grant County sheriff’s deputies in February.

The Central Basin Investigation Team submitted its file this week to the Grant County Prosecutor’s Office in the use-of-deadly-force incident that resulted in the death of 33-year-old Aaron Ammann.

“The prosecutor will determine whether charges will be filed in this case. CBIT does not make charging recommendations,” said Capt. Cameron Clasen of the Ellensburg Police Department. Clasen is the CBIT public information officer.

In an emailed reply to GCJ.news Thursday night, Grant County prosecutor Brandon Guernsey confirmed his office had received the investigation file and was reviewing several statements and about 35 hours of video footage.

“At (this) time, I have not made a final decision,” Guernsey stated.

Records in the case are being maintained by the Quincy Police Department. CBIT investigators included personnel from the Quincy, Ellensburg, and Ephrata police departments; Adams and Kittitas County sheriff offices, Washington Department of Fish and Wildlife and Washington State Patrol. A WSP crime response team processed the shooting scene.

Neither the Grant County Sheriff’s Office or Moses Lake Police Department were involved in the inquiry.

On the evening of Feb. 16, both agencies had deputies and officers on the scene in the 4800 block of Road L.9-NE, a rural location about three miles northeast of Moses Lake. Ammann, who lived in a trailer there, was being sought in connection with an unspecified open police investigation.

A video of the darkened setting showed lights focused on an outbuilding and a large plastic tank. Deputies can be heard talking to Ammann, who was hidden inside the tank and verbally acknowledged he had a firearm.

Deputies are heard telling Ammann that they didn’t want him to get hurt and instructing him to “toss the gun.” Ammann replied, “I’m coming out with it,” and emerged from the tank with what appeared to be a rifle. Deputies yelled “drop the gun” and “put it down,” then fired multiple shots seconds later. It was noted that Moses Lake police officers did not fire their weapons.

An autopsy confirmed that Ammann died from multiple gunshot wounds.

The deputies who discharged their weapons were identified as Cpl. Luis Jimenez and deputies Juan Niebla, Gaven Allison, David Borden, and Jordan Crouch. As standard procedure in use-of-deadly-force incidents, all were placed on paid administrative leave during the initial stages of the investigation.

As required by state law, an independent inquiry was conducted in coordination with the Washington State Office of Independent Investigations and subject to review by the Washington State Auditor’s Office.

The CBIT investigation also included civilian community members who were kept apprised of its status and a family liaison to support Ammann’s family and explain the investigation process. Public updates were issued at least weekly even if there was no new information to share, said Clasen. 

Information regarding an internal investigation was not immediately available from the Grant County Sheriff’s Office.

Ammann had numerous past criminal cases in Grant, Adams, and Franklin counties. In February 2022, he was sentenced in Grant County Superior Court to 19 months in prison after pleading guilty to charges of burglary, theft, and criminal trespass committed in 2021. Prior convictions included drunk driving, possession of methamphetamine, and attempting to elude police.

Note: this article was updated at 10:34 p.m. Thursday, Aug. 20, 2026 to include comments received from Grant County prosecuting attorney Brandon Guernsey.