After deputies shot Thompson with two rubber bullets, Katz said he pushed up off the ground and charged toward the armored vehicle.



Katz said a deputy in the turret of the vehicle shot Thompson, fearing he had a weapon and was going to run past the armored vehicle and fire on deputies behind it.



Deputies later determined Thompson had been unarmed. Katz said it's possible he could have been unconscious until being hit with the rubber bullets.



Thompson's family members say he had diminished mental capacity.



They angrily told the county Board of Supervisors on Tuesday that officers overreacted when there was no immediate threat and that Thompson was kind-hearted and soft-spoken.



"I wouldn't treat an animal this bad," his sister Matrice Stanley told the board. "How is this justifiable?"



Asked later by reporters if she thought race had played a role in the shooting, Stanley said, "I think it did. It's always in the news. This is something that becomes common, which is really sad. Yes it is a factor."



Fatal police shootings of black men have spawned anger and violence around the country, with protesters calling for an overhaul of policing tactics they believe unfairly target minorities in poor neighborhoods.



Katz said he understands why Thompson's family is outraged and wants answers.



"We share that need for those very same answers," he said. "It is our hope that we can instill confidence and reassurance in that effort, and the investigation will be thorough and it will be complete."



Earlier, the Sheriff's Department issued the statement saying, "there is no evidence that Mr. Thompson was in the carjacked vehicle, nor that he was involved in the assault on the deputies" during the carjacking.