Mark Kirby was 52 when he was fatally shot in Billings, Montana, on October 10, 2015. A military veteran, Kirby served 13 years in the Air Force, including a two-year assignment with the Presidential Honor Guard, and later founded and led Montana Veterans Airlift Command, a charity that provided free medical air transportation. At the time of his death he worked as a finance manager at a local car dealership and was a husband and father of three.

The person who killed Kirby was his friend, 64-year-old Jose Cobos, a Vietnam War veteran. Cobos initially said he acted in self-defense but later said he could not remember the events of that night. PTSD was raised during the court proceedings as a mitigating factor; Cobos pleaded guilty to negligent homicide and was sentenced by a Yellowstone County District Court judge to ten years in Montana State Prison, followed by ten years of supervision. The motive for the shooting was never made clear during the legal process.

If anyone knew Mark Kirby or has information about the circumstances of that October night, please come forward.