Four of the five officers who fired their weapons during the incident that left Sean Bell dead attended only one of two mandatory firearms training sessions this year, a group of former police officers said yesterday.

A founder of 100 Blacks in Law Enforcement Who Care, Marquez Claxton, said an internal police document showed that every officer except the undercover detective who first fired his weapon during the shooting last received the training in the early spring. The second cycle ended in October, Mr. Claxton said.

“This shows a lack of supervisory over the unit,” he said. “It is unacceptable. It is outrageous.”

The police commissioner, Raymond Kelly, dismissed the charge as irrelevant.

“Ideally, everyone goes to two cycles, but it’s not unusual for officers not to complete both cycles in one year,” he said.

Police officials refused to confirm whether the officers had missed the cycle, saying only that the officers had received training in 2006, as was required.

Mr. Claxton said the internal document, titled “Shooting Summary Report,” listed the last time each officer had received training.

According to Mr. Claxton, police officer Michael Carey completed the training on March 21. Detective Paul Headley completed it on January 12. Detective Mark Cooper completed it on March 30. Detective Michael Oliver completed it on April 5.

The undercover detective, who hasn’t been identified, completed the second cycle on October 4, Mr. Claxton said.

Most officers never fire their weapon in the line of duty during their careers, so regular firearm training is often their only practice with a lethal weapon.

A former commanding officer of the Firearms and Tactics section of the NYPD, John Cerar, said that during his tenure officers who missed training could lose five vacation days.

“If they could have gone to the range four times a year, I would have been happy,” Mr. Cerar said. “There is a time that is necessary for training — certainly with the transition to the semi-automatic, I thought that the minimum of two cycles is needed.”

Officers go to the Rodman’s Neck Firing Range in the Bronx for the training, which includes classroom lessons about gun cleaning and recent trends in policing, as well as a firearms proficiency test, Mr. Cerar said. The trainers analyze police shootings over the years and create role-play scenarios for the officers, he said.

When he was at the NYPD between 1985 and 1994, Mr. Cerar said the two cycles would deal with different conditions of policing: During one cycle, they might recreate dimly lit scenarios, while in the next they would fire a weapon indoors.

A professor at the John Jay College of Criminal Justice who is a former police officer, Eugene O’Donnell, said: “Frontline operational people don’t have enough training anyway.”

“It’s minimal enough as it is,” he said.”If it doesn’t happen when it’s supposed to happen, that needs to be corrected.”

The president of the Detective’s Endowment Association, Michael Palladino, said a single missed cycle had no bearing on the Sean Bell shooting.

“Whether they did or didn’t have training in 2006, the shooting would have occurred,” he said.