It’s hard to comprehend the tragic chain of events last week that led to the deaths of an innocent bystander and a man involved in a traffic stop by Buffalo police.

Not only does it call for a thorough investigation by both the police Internal Affairs Division and the Erie County District Attorney’s Office, but it offers an opportunity for a thorough examination of Police Department procedures.

This is the sixth time this year that a Buffalo police officer has fired a service weapon at a suspect. Three of the shootings were fatal. Police officials have said the use of such force was justified. But that is enough shooting activity over a short period of time to warrant a serious review of the Police Department’s training, policy and procedures on the use of force.

In last Thursday’s tragedy, police shot a driver after pulling him over on Fillmore Avenue. Mortally wounded, the man managed to drive his SUV four-tenths of a mile before hitting three light poles at Riley Street. One of those light poles fell and hit Ida Murphy, 54, who was waiting to cross the street. She had walked to a nearby store to cash a check, and died from blunt-force trauma.

The incident began when two police officers, assigned to the department’s Housing Unit, pulled over Isaac C. Parker’s sport utility vehicle at about 6:45 p.m. at Fillmore Avenue and Best Street.

The former Marine had three previous convictions for driving while intoxicated. Parker’s brother later acknowledged that he should not have been driving, although he maintained that it was the police action that followed that killed an innocent woman.

Sources told The News that they believe Parker was pulled over for having his high-beam headlights on. The officers later told police officials that they detected a strong smell of alcohol and that the man produced an ID, but not a driver’s license.

One police officer reached into the SUV through the driver-side door in an attempt to turn off the ignition while the other officer opened the passenger-side door, jumped into the vehicle and tried to turn off the ignition.

After the officers sensed the driver putting the vehicle into gear and stepping on the gas, one of the officers shot the driver. Both officers managed to stumble out of the car before it sped off.

Traffic stops are notoriously dangerous situations for law enforcement. Too many officers have lost their lives when “routine” traffic stops turned deadly.

In fact, what would have happened had police not stopped the driver and he went on to kill others, asked Thomas H. Burton, an attorney who represents Buffalo police officers in such incidents?

No one can know the answer to that question. But we do need to find out whether this shooting was justified, and whether police are following proper procedures. So far, the only thing the public knows is that a traffic stop resulted in the loss of two lives.