Whether one shot is fired or 10, police training dictates that it's not the number of bullets but what it takes to stop a threat to an officer's life that matters when a confrontation suddenly spirals out of control as happened in Ferguson, Mo., according to law enforcement experts.
"If somebody's mad or somebody's trying to do something ... you don't even think about it. It just happens so fast that you just react and then you hope like hell that you did the right thing," says Jim Bueermann, president of the Police Foundation, a Washington, D.C.-based non-profit organization that conducts research and training to improve policing.
It's far too early to determine whether the killing of an unarmed Michael Brown, 18, by Ferguson police officer Darren Wilson -- an incident that arose out of a dispute over Brown walking down the middle of the street -- was legitimate, Bueermann says.
But the fact that Brown was struck six times is not necessarily proof Wilson acted illegally, according to Bueermann and David Clinger, a former police officer who is an associate professor in criminology and criminal justice at the University of Missouri-St. Louis.
"Officers are trained to shoot until the threat is no longer presenting a threat," says Clinger, who shot and killed a man while a police officer in Los Angeles in 1981. In conducting book research, Clinger interviewed more than 300 officers who were involved in shootings.
"It's not unusual for police officers to find themselves in a circumstance where they have to shoot multiple rounds because the suspect simply isn't stopping," Clinger says.
Clinger fired one fatal shot that a killed man who had stabbed a fellow officer with a butcher knife in 1981.
There have been starkly different accounts of what happened between Wilson and Brown that early afternoon of Aug. 9. Police have said little other than that Brown tried to grab Wilson's gun when the officer pulled his patrol car alongside and told Brown to move off the street. At least one shot was fired in the vehicle, police say.
Riots that have erupted in the city by a largely African-American community angered by the shooting and what they view as unfair tactics by a nearly all-white police department underscore the need for police training in the key area of cross-cultural sensitivity, says Bueermann, whose non-profit group explores innovative policing methods.
Dorian Johnson, who was with Brown, says the officer shot Brown in the back and then fired several more rounds as Brown turned to face the policeman.
Autopsies have since shown that Brown was struck by six rounds, all in the front, including a fatal round that struck him in the top of his head. Family members argue that this is clear evidence that Brown was trying to surrender. Pathologists say that is not necessarily borne out by the autopsy evidence.
Bueermann and Clinger say the conflicting accounts are evidence that more police departments should require officers to wear video cameras on their uniforms and have them in their patrol cars.
Both say it also is important that officers have non-lethal means available to quell a violent suspect, including a Taser.
They say a crucial question for investigators — and grand jurors who will begin examining evidence Wednesday — will be whether Wilson acted legally in shooting a man who may clearly have been unarmed but may have been physically charging at him.
Officers are trained to gauge the threat and use reasonable force, all in a time frame of a few seconds or less. Brown was 6-foot-4 and weighed nearly 300 pounds. "When you look at the totality of the circumstances, is this a reasonable thing for the officer to have done?" Bueermann says. "And the answer (from a prosecutor or jury) is going to be yes or no. And not everybody is going to like that."
Bueermann says what happened in Ferguson also may demonstrate a need for new ways to train officers in exercising greater empathy for people in their community. He says cultural differences can dictate how people react to police trying to stop them — from walking in the middle of the street, for example — especially if they have long felt persecuted by law enforcement.
Police should be trained in these realities, Bueermann says, "especially if the lens through which (some citizens) see the world is one where police are constantly doing this because of the color of my skin or because of the economic status of my life."
This training can help police tailor their actions in less confrontational ways, perhaps preventing events from spinning out of control, Bueermann says.
"Under this idea, you allow people to interact before you use the authority that the law has invested in you," he says. "Training in these kinds of issues is, I think, lacking in the United States."
Contributing: Jodi Upton