A Family Dollar store security guard who was killed in Flint, Mich., on Friday was shot after telling a customer that her child had to wear a face mask to enter the store, the county prosecutor’s office said Monday.

The argument began when the security guard, Calvin Munerlyn, 43, told Sharmel Lashe Teague, 45, that customers needed to wear face masks in the store, Genesee County Prosecutor David Leyton said at a news conference Monday. She yelled at him, spit on him and drove off, Leyton said. About 20 minutes later, her car returned to the store, and her husband, Larry Edward Teague, 44, and son, Ramonyea Travon Bishop, 23, stepped out and confronted Munerlyn, according to investigators who spoke to witnesses in the store and reviewed surveillance video. Bishop pulled out a gun and shot Munerlyn, Leyton said.

Leyton said Munerlyn was doing his job, protecting others and enforcing a statewide executive order. In Michigan, people are required to wear face coverings in grocery stores. Stores can refuse service to anyone who is not wearing a mask.

“We simply can’t devolve into an ‘us versus them’ mentality,” he said. “We need to make a commitment as a community to do the things necessary to allow us to stay healthy and turn a page on this crisis together. Not for ourselves but for Calvin Munerlyn, who lost his life needlessly and senselessly.”

The shooting is the latest blow in an ensuing battle between government mandates that encourage or require face masks in public spaces to prevent the spread of the novel coronavirus and people who resist the guidelines due to inconvenience or concerns of overreach by officials. The mayor of Stillwater, a small Oklahoma city, and city leaders withdrew a mandate from consideration requiring masks inside reopened stores and restaurants after threats of violence and physical abuse were directed at employees. A day after the Flint shooting, police arrested a man in a city neighboring Flint who allegedly wiped his nose on a Dollar Tree employee’s sleeve after she told him he had to wear a mask to shop, the Detroit Free Press reported.

Michigan State Police are searching for the two men who they think killed Munerlyn. Police arrested Sharmel Teague. All three are charged with first-degree premeditated murder and gun charges. Larry Teague is additionally charged with violating the mandate requiring that people wear face coverings inside grocery stores, which is a misdemeanor, Leyton said.

More than 150 friends and family members of Munerlyn, known by many as “Big Duper,” gathered Sunday at the scene where he was shot, holding candles. At sunset, they released balloons that were blue, black and red — Munerlyn’s favorite colors — into the sky to the clamor of car horns. A GoFundMe for the family has raised more than $195,000, far exceeding its goal.

His wife, Latryna Sims Munerlyn, told The Washington Post he was well known and beloved in the community. “He was so awesome that I’m just honored to have lived my life with him for the past 20 years,” Sims Munerlyn said.

While he was always altruistic for others, his wife said he was most selfless for their six children. “He was with my kids, day in and day out,” she said. “I never woke up without him, I never went to sleep without him. He was just the best father, the best friend.”

County Commissioner Bryant Nolden, who spoke during the Monday news conference, said he often saw Munerlyn training others free of charge at a public gym in Flint. Nolden said he was a mentor to other younger men in the community.

“When I found out what had happened to him, it really broke my heart because I knew what kind of person he was,” Nolden said. “We need to stop the senseless violence in the community. This was totally uncalled for — he didn’t bother a soul. All he wanted to do was take care of his family, and he always had his kids with him.”

When Nickolas Harrison, who looked up to Munerlyn, told his friend of 15 years that he wanted to follow his career path in security, Munerlyn gave him one glove of a set that he often wore on the job, Harrison told The Post.

Harrison still has his black Nike glove, a keepsake of a friend who was protecting others when he died, he said.

“My friend Duper was killed for telling a lady she has to put a mask on to come in the store,” he said, “which could save her life or the life of others.”

Family Dollar’s website says store employees may wear face coverings, but there is no requirement listed for customers.

Randy Guiler, a company spokesperson, called the shooting “tragic” in a statement given to The Post.

“We will continue to cooperate fully with local authorities on their investigation,” Guiler wrote. “As always, we are committed to ensuring a safe environment for our associates and customers. Out of respect for the family’s privacy, we are not commenting further at this time.”