The case began with a report of property damage. On the evening of March 18, two officers from the Sacramento Police Department were dispatched to investigate a complaint that someone was breaking vehicle windows.

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Local clergy and community members linked hands after a City Council meeting on Tuesday.CreditMax Whittaker for The New York Times

A helicopter from the Sacramento County Sheriff’s Department was also hovering over the scene looking for a potential suspect when it identified a man with a crowbar heading toward a nearby house.

A few minutes after responding to the call, with the apparent guidance from the sheriff’s helicopter, the city police officers spotted Mr. Clark, who they said ran from them. They followed him into the backyard and ordered him to show his hands, police video shows. Seconds later, in the dark, one officer shouted, “gun, gun, gun, gun!” and they shot 20 times at Mr. Clark. The officers believed Mr. Clark had a weapon and opened fire “fearing for their lives,” according to a police statement.

The entire encounter lasted roughly 10 minutes. The officers looked for a gun but all they found was a cellphone.

“Everybody knows that we’re getting killed regularly out here; that’s the buildup to this,” said Tanya Faison, who founded the local chapter of Black Lives Matter.

“It is very important that police officers not kill the black men when they are out rampaging and committing crimes.” said a police officer from the district.

Don’t do the crime if you can’t do the time. Maybe he shouldn’t have been out there in the middle of the night with a crowbar smashing in car windows? No that thought doesn’t occur to blacks.

“He was a good boy, he didn’t do nothin!” said a family member