At the Pride March last weekend, fireworks set off in Washington Square Park sounded to some like gunshots, leading to a terrifying, chaotic stampede of hundreds of people.

“I ran in a panic, but didn’t understand what was happening,” said Marcela Paz Jara Martinez, who is visiting New York this summer from Chile. “I just looked for a place to hide. I saw a bunch of people on the floor being hurt […] I thought I was going to die.”

A week earlier, Carly Triche was on a downtown train stopped at West 4th Street when word quickly spread -- falsely, it turned out -- of a gunman. “Screaming, crying, I heard a lot of ‘holy shit, oh my God,’ that sort of panic,” she said. Triche joined a mass of people and fled the station to the street.

And in May, at the Barclays Center, a similarly false report of a shooting led to yet another stampede. Sixteen people were injured, police said.

Mass shootings in the United States are so commonplace that the very fear of them is manifesting in panics like these, according to mental health and public safety experts. During July 4th weekend, given the possibility of mistaking fireworks for gunshots and the fact that the weekend often sees a spike in violent crime, conditions can be ripe for frightening misunderstandings.

“I do feel like our entire country right now is traumatized by the fact that it feels like a mass shooting can happen anywhere at any time,” said Jonathan Metzl, a psychiatrist and sociologist who is director of the Department of Medicine, Health, and Society at Vanderbilt University. “So I would say there is some sort of nationalized trauma happening right now.”

He said characteristics of PTSD usually found in those who have personally experienced a traumatic event like war -- clinically known as exaggerated startle response and hyper-vigilance -- are now seen in the broader population. And the traumatizing effects of the global pandemic, plus the increase in both gun sales and mass gun killings, have led to what Metzl described as feelings of hopelessness.

“You would think that given how many people are having this experience, society would mobilize to make people feel safer,” he said. “And in a way we’re seeing the opposite, we’re seeing the breakdown of the kind of institutions that would ensure safety in an otherwise civilized society.”

Metzl cited the U.S. Supreme Court’s recent ruling that is likely to mean more people are allowed to carry concealed weapons in public as stoking further fears. In fact, that court decision was on Triche’s mind when she was running out of the subway station. “I just assumed I was going to get shot in the back of the head,” she said. “I have a 2-year-old [son]. They say you see your life flash before your eyes -- I saw his life flash, and everything I would miss.”

The NYPD said in a statement that although someone called them to report a man with a firearm on the subway, in reality the panic began after a man strangled and punched a 35-year-old victim on a southbound E train. There were no shots fired, and a gun was not found at the scene.

Panic, like other human behaviors, is contagious. Instances of mass hysteria have been documented as far back as the middle ages, according to Dr. Charles Marmar, who leads the Department of Psychiatry at NYU Langone Health.

Marmar said distress signals spread similarly because humans are pack animals.

“We depend for our survival on rapid communication of threat, and the threat signal can spread very quickly through the herd,” he said.

That’s what appears to be happening in these recent cases in New York. With pandemic restrictions falling away, New Yorkers are gathering in large crowds again, possibly leading to more such panics -- like on July 4th weekend, when fireworks can easily be mistaken for gunshots.

“People do appear to be on edge,” said Brian Higgins, a former police chief in New Jersey and a professor at John Jay College of Criminal Justice. “But that doesn’t help you in an emergency situation.”

Higgins' advice for attending events in crowded spaces: Be aware of your surroundings. Pick out a location for meeting the people you’re with in case of an incident. Note exits other than the entrance where you arrived, and identify things to hide behind in case of a shooting.

If you’re not sure if there’s just been a shooting, Higgins said, “and you’re nervous, slowly start walking to a location of safety, or best-case scenario, an exit.”

Even if one gets out, though, and even if there turns out not to be a threat, the panic itself can be traumatizing for those who experience it. Jara Martinez is still upset from her experience at Pride, and she is avoiding crowds for now.

“I’ll tell you I’ll never wear heels or sandals again,” she said. “From now on, I have to wear shoes, because I don’t know when I’ll have to start running.”