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Prosecutors on Wednesday said a Charlotte, N.C., police officer acted appropriately in the September fatal shooting of a black man that sparked violent protests in the city, as a two-month investigation showed the man, Keith Lamont Scott, was holding a loaded gun.

Brentley Vinson, an officer with the Charlotte-Mecklenburg Police Department, won't be criminally charged, Charlotte District Attorney R. Andrew Murray said at a Wednesday press conference.

Mr. Scott's family has said he was holding a book while waiting for his child at a bus stop on Sept. 20. But prosecutors said "no reading book was found" in Mr. Scott's SUV, and radio traffic, video surveillance and interviews with police officers on the scene indicate he was holding a cocked and loaded handgun, Mr. Murray said.

"All of the credible and available evidence suggests that [Mr. Scott] was in fact armed," he said.

Mr. Vinson, a black officer with two years' experience on the force, was one of two officers conducting surveillance Sept. 20 in an apartment complex parking lot in suburban Charlotte. The officers were parked near Mr. Scott, 43 years old, and saw that he had marijuana and a gun, according to police reports.

The officers put on vests that identified themselves as police, and were joined by other officers, according to police and to dash-cam footage. The officers approached Mr. Scott's SUV and told him 10 times to "drop the gun," the prosecutor said. Police dash-cam video shows Mr. Scott backing away from the SUV with his hands down, just before shots are fired by Mr. Vinson.

Investigators analyzed the dash-cam, body-cam, cellphone footage and other video, but no recordings "clearly capture Mr. Scott's hands," Mr. Murray said.

However, the prosecutor showed newly released video surveillance footage of Mr. Scott taken at a nearby convenience store just before the shooting, with a bulge at Mr. Scott's ankle that the prosecutor said was consistent with the shape of the ankle holster and gun found at the scene.

The prosecutor also played radio traffic recorded before the shooting of officers discussing the gun, and showed Facebook messages in which the person who says he illegally sold Mr. Scott the gun expresses remorse.

The Scott family has said Mr. Vinson and the other officers failed to use all the resources available to them to de-escalate the encounter with Mr. Scott, who had a traumatic brain injury. The family has also said officers could have asked for help from Mr. Scott's wife, who was nearby recording the incident on her cellphone and yelling at police to leave Mr. Scott alone.

The Scott family lawyer couldn't immediately be reached for comment Wednesday.

Mr. Murray, the district attorney, said more than 2,000 hours of state investigators' time had been invested in the review of the shooting. The decision not to prosecute Mr. Vinson was supported by all the top prosecutors in his office, he said.

"I'm asking the community to take a collective pause," he said. "It's a justified shooting based on the totality of the circumstances."

The city of Charlotte is increasing police presence in the coming days, as violent protests crippled the downtown in the days following Mr. Scott's death. Organizers of Charlotte Uprising, a community group calling for police accountability, scheduled a Wednesday night protest in front of the county jail downtown.

It is rare for an officer to be charged in connection with an on-duty shooting, as the law gives officers the benefit of the doubt in most cases, legal experts say.

An estimated 1,000 people are killed annually in confrontations with police, according to Philip Stinson, an associate professor of criminal justice at Bowling Green State University in Ohio.

Eighteen officers were charged with murder or manslaughter in fatal on-duty shootings in 2015—the most in any year going back a decade, Mr. Stinson said.

Write to Valerie Bauerlein at valerie.bauerlein@wsj.com

(END) Dow Jones Newswires

November 30, 2016 12:35 ET (17:35 GMT)

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