Editor's note: Eugene O'Donnell, a former New York City police officer and prosecutor, is a professor of law and police studies at John Jay College of Criminal Justice.
(CNN) -- Shortly after 9 a.m. on Friday, a man identified as Jeffrey Johnson shot a former co-worker outside the Empire State Building with a .45-caliber weapon. A courageous civilian saw what happened and alerted two NYPD officers. After the police caught up with Johnson, he pulled his weapon out of a bag and pointed it at the officers who had been performing counterterrorism duties. The officers fired 16 shots, killing Johnson. In the exchange of fire, nine bystanders were injured.
As a rule, it takes a lot to get NYPD officers to fire their guns at anyone. Despite a handful of isolated, but highly publicized, exceptions to this rule when officers have shot unarmed individuals over the past decade and a half, New York's 35,000-officer force remains a worldwide model of firearms restraint and veneration for human life.
The nation's largest police department instills in its officers that the decision to fire a weapon is momentous and should only be considered after every reasonable alternative has been exhausted. Only when officers feel that a suspect is a clear and imminent danger to them or others can they resort to using their firearms. Then, they must take care to not needlessly endanger innocent people who might be in the way.
In rapidly unfolding and completely unpredictable situations, assessing the need to use firearms is often a split-second decision. It can mean the difference between life and death. Officers have to sift through confusion, fear and fragmented information.
In the incident outside of the Empire State Building, it is made more difficult because the street is one of the busiest in America. The officers had to take into account the risk of the gunman hurting potentially many people in the vicinity were he not stopped.
When New York officers do use firearm, it is a matter of great importance to the department. Shootings are vigorously reviewed. Officers are questioned thoroughly and can be ordered to undergo additional training. They can be disciplined and even terminated. The police department pores over each shooting and tries to glean insights that can help better train cops. The message is clear: Firing a gun must remain the rarest of rare events.
For prosecutors and police executives reviewing events when all the facts are known afterward, it is a different story. Officers can be criticized for too much action or for too much restraint when things don't go well.
Fortunately, in the incident today, the bystanders who were shot were not seriously hurt.
Street officers are always interested in better ways to handle unpredictable situations, and police departments everywhere cannot provide enough quality hands on training for front line cops. Excellent training in firearms restraint is a vital tool that has helped drive down NYPD shootings over time. In 1972, New York's finest were involved in almost 1,000 incidents in which firearms were discharged; in 2010, that number was just 92. Good thing, too, because no matter the training or innate restraint of the police, there really is no safe way to deal with shootings in a crowded city. Ultimately, the outcome is always uncertain.
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The opinions expressed in this commentary are solely those of Eugene O'Donnell.