Increasingly hysterical and despondent, he led the police on a chase through Missoula’s icy streets that ended when his car died along an on-ramp. He slapped Ms. Daniel with the back of his hand a few times during the ride, she testified, and alternately yelled, cried, punched the steering wheel and apologized to her. He had previously been convicted on drug charges and told Ms. Daniel, “I’m not going to do this again.”

“I knew he was talking about dying,” she testified.

Corporal Kelly, a 12-year veteran of the Missoula police, was the first to approach the car. In videotapes and transcripts from that night, he was empathetic and understanding until the moment he shot Mr. Williams. He urged Mr. Williams to calm down, insisted that he had other options and told him that he did not want to shoot him.

When Mr. Williams yelled that he had reached a dead end, Corporal Kelly said, “Just talk to me, man,” according to the transcript.

Several times, Mr. Williams urged the police to shoot him, once pointing to his head.

“Kill me right now, and it’s over,” he told them.

“O.K. well, I can’t do that,” Corporal Kelly responded. “That would be murder.”

“Right here, right now, it’s over,” Mr. Williams said.

“And if I don’t?”

“It’s gonna get ugly.”

Had Mr. Williams been alone, Corporal Kelly said, the police would probably have backed off and negotiated from a distance. But they could hear Ms. Daniel whimpering in the car, and said Mr. Williams had yelled that he was holding her hostage. Although he turned out to be unarmed, his mother had told the police that he might have a knife, scissors or pepper spray.