“I think he felt the walls closing in and realized that it was best to turn himself in,” Mr. Armstrong said. He said he spoke with Mr. Wilbourn before he was taken for questioning.

Image Tremaine Wilbourn Credit... Memphis Police Department/Reuters

“He wanted to make it a point to say that, one, I am not a cold-blooded killer and, two, I am not a coward,” he said.

Mr. Wilbourn faces a charge of first-degree murder in the shooting of Officer Bolton during a traffic stop on Saturday night in southeast Memphis. The police said Officer Bolton, 33, was killed after he interrupted a drug deal.

Officials said Mr. Wilbourn was a passenger in a Mercedes-Benz that Officer Bolton approached because it was illegally parked. After a brief struggle with the officer, the police said, Mr. Wilbourn shot him multiple times and fled.

The driver, who also fled, surrendered to the police after a standoff on Sunday, and was later released without charge. Detectives found digital scales and a small bag of marijuana in his car, according to police officials.