Police said the 60-year-old was trying to stop two men from stealing the beer when he was stabbed in the chest.
Ganns was taken to Hemet Valley Medical Center, where he was pronounced dead.
The suspects are described as white or light-skinned Hispanics, 18 to 28 years of age, with medium builds and between 5 feet, 6 inches to 5 feet, 10 inches tall.
Police said one or both of the suspects have head and neck tattoos.
Anyone with information is urged to call Hemet police at (951) 765-3897.
City News Service contributed to this story.
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