RALEIGH, N.C. — There is no doubt that officers surrounded him. That they shouted at him. That they shot him. But a crucial question about the fatal confrontation between Keith L. Scott and police officers in Charlotte, N.C., has always been whether Mr. Scott was wielding a gun.

On Wednesday, in a 40-minute news conference that at times took on the feel of a courtroom argument, R. Andrew Murray, the district attorney for Mecklenburg County, laid out a case that Mr. Scott, who was black, had a gun in his hands and had not heeded warnings to drop it when he was shot and killed.

“It’s a justified shooting based on the totality of the circumstances,” Mr. Murray said. No charges, he said, will be filed against the officer, Brentley Vinson, who is also black.

Mr. Murray made his case with an elaborate presentation of videos, enhanced digital images and other evidence, a reflection of the increasing sophistication of prosecutors who must also sway a public skeptical of police accounts of fatal shootings.