“There is this huge misunderstanding in this country about the rules surrounding police officers’ use of deadly force,” said Jim Bueermann, a former Redlands, Calif., police chief who is now the president of the Police Foundation, a research group. “People just say, if a person was unarmed, why would an officer have shot him or her?”

In fast-moving situations, police protocol often leaves little room for error.

Officers usually have a round chambered in their sidearms. And experts say they are generally taught to draw their guns when they feel they or someone else are in imminent danger. Even for many traffic stops, officers keep a hand on the weapon while it is in the holster.

Mr. Bueermann said he believed many officers were quicker to pull their guns than they would have been a decade or two ago. “There is constant messaging to police officers about the dangers of their jobs,” he said. “There’s a really common adage in policing: It’s better to be tried by 12 than carried by six.”

He also questioned whether Officer Noor might have accidentally discharged his weapon — a far more common event than many realize, he said.

What made this shooting particularly bizarre, to veteran police officers, was that Officer Noor fired at close range past his partner. Many officers would be furious or unnerved if a partner shot across them in any situation short of being attacked, said Vernon J. Geberth, a former New York City police commander and the author of “Practical Homicide Investigation,” a widely used textbook.

The officer’s partner might well be thinking, “You could’ve shot my head off,” Mr. Geberth said.

Personal Effects

Barefoot, on a beach in Kona, Hawaii, exchanging vows under a wooden arch trellised with Tibetan prayer flags onto which their guests would add prayers of their own: That was the plan. The wedding was set for Aug. 17.

Mr. Damond would wear a bright blue suit with an open-collar white shirt. Following tradition, he had never seen Ms. Damond’s dress.