The body camera footage is from last Wednesday's confrontation between Officer Christopher Simas and the suspect David Molina.
Investigators say Molina refused 31 commands to put up his hands or stop running. Both men struggled when Officer Simas tried to handcuff Molina.
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Police say Molina grabbed the trigger of the officer's rifle, and fired several times. Moments later, Simas shot and killed Molina.
Monday Napa Police Chief Robert Plummer explained why his officer carried such a powerful weapon.
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"Knowing that they are going to a person with a gun call, they use the most accurate that we have in our arsenal. That being the rifle."
Police confronted Molina after someone reported he threatened them with a gun. Investigators found a gun at the scene and they believe it had been in Molina's waistband.