Civilians occasionally find themselves in harm's way when officers use deadly force, though usually only a handful of times annually. When that happens, a rigid process of investigation is set in motion - and the police department can reasonably expect a lawsuit.
The latest episode came when police say a man disgruntled over losing his job a year ago shot a former colleague to death and pointed his weapon at two police officers in the shadow of a major tourist attraction.
He apparently wasn't able to fire before police killed him, one firing off seven rounds and the other nine. Bystanders suffered graze wounds, and some were struck by concrete gouged from buildings by the bullets, authorities said. At least one person said he was actually hit by a bullet.
Robert Asika, a 23-year-old tour guide who was hit in the right arm, said he was "100 percent positive" he was shot by a police officer.
A witness told police that laid-off clothing designer Jeffrey Johnson fired at officers, but ballistics evidence so far contradicts that, authorities said.
Police released dramatic surveillance footage later on Friday. The video shows a calm scene with people milling about on the street. Johnson comes into view walking quickly down the street, followed by two police officers. He stops, wheels around and points a gun directly at the officers. The officers fire at Johnson and he quickly falls to the ground. The video shows nearly a dozen bystanders running, including a little boy and girl who were just feet away from Johnson.
During any shooting involving police, the officers who fired their weapons are first interviewed by prosecutors to determine whether anything criminal took place. The officers are placed on desk duty while the probe is completed, and if no criminality is determined, they are interviewed by the department's internal affairs arm.
Meanwhile, police will try to account for every shot fired, every shard of concrete sprayed and every bullet fragment by interviewing witnesses and doing ballistics reports at the scene. Johnson was hit at least seven times, chief spokesman Paul Browne said.
If bullets fired by police or fragments struck civilians, then the officers were also lucky to be alive, since bullets could have boomeranged in their direction, said Eugene O'Donnell, a professor of police studies at the John Jay College of Criminal Justice.
O'Donnell, a former police officer and police trainer, said the shooting officers found themselves in a situation that police dread - because of the danger that bullets can ricochet in crowded settings.
"Picture 50 terrible places in America to have a shooting, and this would make the list for sure," he said.
He said officers are trained to fire only as a last resort and must fire multiple shots because only one in five generally hit the intended target.
He said it was "not a choreographed event where the officers can look at each other and say, 'You fired three? I'll fire two.'"
And sometimes, the officers fail to disable a gunman even when they hit him, O'Donnell said.
Those injured can sue the city for damages for personal injury if they can prove officers did not exercise care reasonably required under similar circumstances. The family of a woman killed by police in 1993 received nearly $4 million.
The woman, Bonnie Vargas, was taken hostage by a gunman fleeing a bank robbery in Manhattan. She was shot three times by police when they exchanged fire with the hostage taker. The appeals court noted that the patrol guide said police in a hostage situation could not fire a weapon "when doing so will unnecessarily endanger innocent persons."
The court also wrote: "The immunity afforded a municipality for its employee's discretionary conduct does not extend to situations where the employee, a police officer, violates acceptable police practice."
O'Donnell said it was likely lawyers will test the adequacy of Friday's police shooting.
"I'm sure there's people chasing the ambulances into the emergency room as we speak," he said.
He predicted the city would undertake a careful study of the events, as well.
"The NYPD will take it seriously," he said. "The cops are authorized by law to defend themselves, but not to be reckless. You've got to be careful you don't unnecessarily endanger other people."
Defense lawyer Ron Kuby noted that bystanders shot in crime-ridden neighborhoods do not usually attract much attention.
Citing reports that the suspect was walking away when police confronted him, he said he and other activists "will wonder if it was the best police strategy to open fire in the most densely populated place on the planet."
For civilians, O'Donnell recommends they find something big and sturdy to hide behind if they hear gunshots.
"Be creative in taking cover," he said. "Always find something to duck behind, a fire hydrant, go into the gutter, in the curb."
He advised against running: "You're not going to outrun a bullet."