Martín Quezada was on a Zoom call with constituents when he heard loud bangs echoing across the open-air mall below, and the Arizona state senator rushed to his third-floor apartment window. He saw people fleeing and a man carrying a long object about 50 yards away, walking toward his building.

“My first thought was, ‘Those are gunshots,’ ” said Quezada, who represents the 29th Legislative District, which includes the Glendale mall. “But I was hoping that it wasn’t gunshots. I was hoping that it was something else, like firecrackers.”

The object in the man’s hands was a black assault-style rifle, according to police, the type of gun that has been used in many of the nation’s worst mass shootings. In this case, the alleged shooter was Armando Hernandez Jr., 20, who surrendered to police after three people were shot. He allegedly told authorities that he had intended to shoot 10 people, in part to get back at society because he had been bullied all his life. Two of the victims suffered non-life-threatening injuries and a third, who was in critical condition, remains hospitalized.

An attorney representing Hernandez did not respond to a request for comment.

The incident last week happened in a popular shopping and entertainment district that was just beginning to open up after coronavirus restrictions were lifted. And it was a jarring reminder that although much of the United States is transitioning from some degree of quarantine, a return to normalcy probably will be accompanied by the return of something that has become an all-too-regular part of American culture: the mass shooting.

The assault in Glendale didn’t qualify as a mass shooting under most definitions because no one was killed, in large part because the mall was not crowded — The Washington Post’s mass shootings database tallies attacks that kill four or more people, while some groups, including the Gun Violence Archive, consider mass shootings to be those that injure at least four people. There were 13 shootings in the United States in 2019 that killed four or more people, according to Post data, and there have been two thus far in 2020, a workplace attack in Milwaukee that left five dead in late February and a convenience-store shooting that killed four lives in Springfield, Mo., in March, just before the nation reacted to the pandemic and shut down.

One reason for the lull in recent months, experts say, is simply that people have not been getting together en masse, creating fewer opportunities for such atrocities. Schools have been closed, church services have moved online, bars and restaurants have gone dark, many businesses have been closed, and concerts and events have been postponed or canceled.

But experts warn that the realities of the coronavirus pandemic could lead to a surge in indiscriminate public violence as the nation reopens and people begin to gather again. The widespread loss of life and the economic collapse, unemployment, isolation and lack of access to mental health services could create the conditions for the types of personal turmoil that give rise to such attacks.

“There is reason to be concerned that this is kind of a perfect storm of people in crisis,” said Jillian Peterson of Hamline University in St. Paul, Minn., who co-wrote “The Violence Project,” a study of commonalities among mass shooters.

James Densley, a professor of criminal justice at Metropolitan State University who also co-wrote the study, said mental health challenges almost certainly are being exacerbated by the pandemic.

“You’ve got a lot of alienated and frustrated individuals who have been cooped up at home and perhaps have been using this time to be online, getting radicalized,” Densley said.

In the immediate aftermath of the shooting in Glendale, Quezada rushed downstairs to see civilians racing to aid the injured, followed by paramedics. Bullets were lodged in concrete wall storefronts and left windows shattered.

“I still wasn’t sure that I had seen what I saw,” Quezada said. “I still couldn’t comprehend. You just want there to be some other explanation.”

Soon after, Glendale Mayor Jerry Weiers arrived to address the news cameras with a familiar refrain.

“Obviously, this is not the norm. This is isolated. It’s not normal for the city of Glendale,” he said. “We’re dealing with somebody who obviously had issues.”

In their research, Densley and Peterson recognized a pattern in how local officials respond in the hours after mass shootings. The tendency is to frame the incident as an isolated one — an outlier, as opposed to a symptom of a failing public safety net for at-risk people.

“You rarely hear politicians say, ‘You know, people are hurting in our community and people are losing their jobs and they’re struggling and we’ve lost our sense of connection,’ ” Densley said. “If you say anything like that, there’s a sort of fear that you’re throwing yourself under the bus. And instead, if you can just point to individual behavior and say, look, this person’s an anomaly, that’s not who we are or who we stand for, and that’s not what people do around here, you create that kind of ‘us and them’ dichotomy and you absolve yourself of any responsibility. And that’s not to say that the offender should be absolved of that responsibility. They are ultimately responsible.”

Researchers say all of the life experiences and traumas that many mass shooters have in common are occurring in greater numbers nationwide right now, with such indicators as more calls to domestic violence hotlines and increasing depression and anxiety.

The adolescent psychology community has begun raising concerns about the mental health of the nation’s children upon their return to school, said Deborah Weisbrot, a pediatric psychiatrist at Stony Brook Children’s Hospital in New York who for a 2008 study interviewed dozens of students who made shooting threats.

“We haven’t been massing, so there haven’t been mass shootings, and we haven’t had school, so we’ve had two months for the first time in decades where there’s been no gun violence in schools,” she said. She noted that doctors are seeing more “depression, suicidal ideation, self-mutilation.”

“What is the impact on so many students who’ve had losses?” Weisbrot said. “And we’re seeing kids who are not tolerating well the social isolation.”

Experts say a spring surge in gun sales across the United States also is troubling. The federal government processed 2.9 million background checks for firearm sales in April, the fourth-highest month since 1998, according to the Trace.

“For a while, people were buying a lot of guns after toilet paper, and it’s safe to assume a portion of those guns will not be properly secured,” Weisbrot said. “It’s hard to imagine that there aren’t going to be significant impacts from all of this when we begin to mass again.”

Quezada said that although the Glendale shooting mercifully stopped before more people were injured and it was a stroke of luck that no one was killed, it was obvious that it was related to the reopening of gathering places, which is an ominous sign.

“The fact that we were only open for a few hours as a state and it happened already, and it hadn’t happened for the last several months throughout the nation, says a lot about how serious this problem is and how we fail to address it,” Quezada said. “It may not happen here again, but it could absolutely happen in the next town or in the next school district over. In that sense, it’s not a unique situation.”