FAIRFIELD — When Officer Sean Fenton had to make a split-second decision Tuesday morning to draw his gun when confronted by Christopher Andrews outside his Mountain Laurel Road home — an encounter that turned fatal when Andrews was hit by shots fired by the officer — Fenton became one of only a few Fairfield officers to have discharged a handgun at another person in the line of duty.

Most of the department’s officers will make it through their entire career without ever having to even take their gun from its holster while on duty in this traditionally quiet town.

But Lt. James Perez has personal insight into the fateful choice Fenton, a Fairfield officer 26 years, was forced to make this week. It was Flag Day, June 14, 2002, and Perez, just promoted to sergeant, had just started a midnight shift when he heard a fellow officer’s agitated radio call about a possible sniper.

Perez sped to the lower Black Rock Turnpike address of what was then Boston Billiards, across the street from BJ’s Wholesale Club.

Officer Chris Rubis “was a low-key guy,” Perez said, “and he was yelling into the mike. I flew down Kings Highway.”

At that point, he recalled, the adrenaline was pumping fast. As he pulled up to address, Perez said he was already mentally going over the best place to position himself. “I get out of the car and I’m looking at (Rubis), who is squatting behind a car, pointing his gun toward the suspect,” Perez said.

Rubis had already shot the suspect at least once. Perez yelled to Rubis, but Rubis didn’t hear him. “I had to run up to him and touch him for him to realize I was there,” he said.

Perez then ran behind a Bronco to get closer to the suspect, who was standing in the parking lot, a gun in his hand, so he could try and talk to him. Shots ring out, and Perez hit the ground. “All I could hear was the ‘plink, plink’ of shells hitting the asphalt,” he remembered. Perez demanded the man drop the .44 magnum he was holding. Instead, the man started firing again at Rubis.

“We were about 20 yards away,” Perez said, and then the man “was holding the gun sideways, pointing it at me.” Perez fired his gun, hitting the gunman — who had been smoking PCP-laced marijuana — in the shoulder and knee. “He drops to the ground, but he still wouldn’t let go of the gun.” Finally, the man did, and Perez said he realized by then there were nine other cops in the parking lot with guns trained on the gunman, who was taken into custody.

At that point, police protocol for shootings was initiated with Perez, Rubis and Officer Peter Stansfield turning over their guns as the investigation began.

“I know exactly what Sean is going through,” Perez said of the fatal shooting outside Andrews’ Mountain Laurel Road home. “It’s a surreal feeling, things are happening so fast.”

When an officer is engaged in an active-shooter situation and fires his weapon, Peres said the officer initially experiences tunnel vision, “all you see is that person” he said. Next is what he called “time dilation” with everything happening in slow motion and the third is auditory exclusion — as when Perez said all he could hear was the noise of shells hitting the ground.

“You’re so hyper aware, and focused on the shooter, all these other things just disappear,” he said.

After the shooting, Perez was put on mandated administrative leave. “They ask you to stay home, to decompress,” he said, and meet with a psychiatrist, who has the authority to clear an officer to return to duty. “I think it was four days for me,” he said.

Perez said, when he first became a police officer, he came to terms with the reality there could come a time when he would have to use his gun — and possibly kill someone. “If it’s going to be them or me, it’s going to be them,” he said.

Fairfield officers are trained to handle situations, Perez said, where a “suspect” — actually, a paper target on a rail, armed with a knife — is just 21 feet away. The target then begins to move toward the officer, he explained. Some officers were not event able to unholster their guns before the training suspect was almost on top of them, Perez said.

It is difficult job, Perez said, and not everyone can handle the pressure.

In the late 1980s, Officer Ronald Thompson was called to a home to assist employees from Bridgeport Mental Health, who were trying to bring a schizophrenic man to the hospital. Thompson went to an bedroom upstairs, and was confronted by the man, who swung an axe at him. Thompson fired his gun, killing the man. Thompson lated decided to take early retirement from the police force, and filed a lawsuit against the deceased man’s family.

Whenever there are news reports of an office involved shooting, Perez said, his mind travels back to that night. But it isn’t something he talks about much, he said, even now as he travels across the country leading active-shooter training seminars for law-enforcement agencies.

“Maybe we feel like no one’s going to understand,” Perez said.