Jose Arreola walked into a Southern California gas station to buy Mentos on a Friday night in March and still can’t shake off what happened next. After he paid for the mints and placed them in his left jacket pocket, an off-duty police officer behind him pulled out his handgun, pointed it at his feet and accused him of stealing them.

“It made me angry,” Arreola, 49, said Monday. “I felt this fear and thought of my wife. My wife might become a widow tonight.”

The night started when Arreola, who was on his way to a club with his wife, pulled into a Chevron station in Buena Park in Orange County, California. He got $60 (U.S.) out of an ATM, then remembered that his wife had asked for mints.

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Standing in front of the cashier, Arreola scanned a row of candy bars, sweets and gum before reaching for a roll of Mentos. “How much are these?” Arreola asked the man behind the counter. The cashier told him they were $1.19.

The transaction on March 16, which was recorded by the gas station’s security camera, was entirely uneventful until the off-duty officer, who works for the Buena Park Police Department, entered the store. He missed the part when Arreola handed over $20 for the Mentos.

“Hey, put that back,” the officer said as he lifted his sweatshirt and pulled a handgun from his waistband. “Put it back. Police officer.”

“I just paid for this,” Arreola responded.

The misunderstanding was resolved in about 35 seconds — the officer put away his gun and apologized — but it was long enough to taint Arreola’s perception of the police and to land the officer in an internal Police Department investigation.

“You can’t help but look at all these Facebook videos of cops doing bad things,” said Arreola, who went public with his story Friday in an interview with The Orange County Register. “The way he cocked his gun, I thought he was going to shoot me if I did any wrong move.”

Arreola said that after the encounter, he filed a complaint with the Police Department against the officer, who has not been identified. The department offered last week to settle the dispute, Arreola said, but he declined the deal because the amount would have only covered his legal fees.

Across the United States, police departments have come under intense scrutiny in recent years over the use of force and treatment of minorities. The worst actions by police officers are sometimes captured on cellphone video and quickly shared on social media, fuelling a distrust toward law enforcement.

John DeCarlo, a former police chief and an associate professor of criminal justice at the University of New Haven in Connecticut, said he reminds police officers to treat everyone they encounter with respect, from mundane interactions to very intense ones.

Everyday encounters, such as seeing an officer in a gas station, shape people’s overall perceptions of the police, he said. “We have an innate fear of police to begin with,” DeCarlo said. “It’s about treating people how you want to be treated.”

DeCarlo was startled as he watched the security footage of the off-duty Buena Park police officer. “Oh my goodness,” he said as he watched the officer retrieve his gun. “Holy mackerel.”

He said the officer violated the most basic rules governing the use of force by the police. No matter the situation, officers should issue verbal commands first. Pulling out a gun should be a last resort.

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“What the officer did was incredibly inappropriate,” he said.

Corey S. Sianez, the Buena Park police chief, said he was also troubled by the officer’s actions. “I want you to know that after I watched the video, I found it to be disturbing, as I’m sure it was to you,” he said Friday on Facebook.

Sianez said the actions by the officer were under review. He did not respond to an email Monday asking whether the officer was still on active duty or if he had been placed on leave during the investigation.

“I can definitely assure you that our investigation will be thorough,” he said. “If the officer is found to be in violation of any policies and procedures, he will be held accountable.”