At least 12 people were injured after a large crowd in New York City’s Times Square fled in panic on Tuesday night, when they mistook the sound of backfiring motorcycles for gunshots.

The confusion brought Tuesday night’s Broadway performance of To Kill a Mockingbird at the Shubert Theater to an early end, as people both inside and outside the theater were caught up in the incident. The widespread fear and confusion felt in Times Square comes just days after 31 people were killed in mass shootings in El Paso and Dayton, Ohio.

Celia Kennan-Bolger, who plays Scout Finch in the production, wrote on Twitter that she was giving her last speech in the play when people outside tried to get in to the theater, believing there was an active shooter nearby. Audience members who heard screams from outside and banging on the doors also tried to flee the theater, she said.

“It was terrifying for us because we didn’t know what was happening or what to do,” she wrote. “I’m still processing the whole experience but all I can think about are the young people who’ve had to go through the actual thing.”

One audience member said a crowd in the theater ran out of the emergency doors. “The street was all running, so I ran until no one was running,” he wrote.

This is not the first time Times Square has been the site of deadly incidents. In 2010, a terrorist attack was averted after police found a car bomb in a vehicle in Times Square. One man, Faisal Shahzad, was charged with terrorism-related crimes and sentenced to a life term in prison in 2010. A driver who hit pedestrians in Times Square killed one woman and injured 22 others in 2017 (though there was no sign the incident was an act of terrorism).

On Tuesday, the loud noises caused people to flee the area in large numbers. Those injured in the ensuing stampedes sought treatment at local hospitals, an NYPD spokesperson tells TIME. The most serious injuries involved a woman with a broken wrist and a man with a fractured kneecap.

People out on the street said the sounds were similar to gunshots. One woman told NBC New York that she became stuck inside a theater, and was separated from her daughter amid the crowd. “Everyone thought there was a shooter coming down the streets,” she said. “I thought I was going to watch my daughter get shot down in front of me.” Others wrote of the fear and hysteria, as well as the response to shooter drills they’d undertaken.

New York City police later confirmed there was no active shooter in the area. The gunshot-like sounds came from a group of six men revving the engines on their dirt bikes, police said.

“Please don’t panic,” the NYPD wrote on Twitter.

Gideon Glick, another actor in the show, who plays Dill Harris, wrote that “the audience started screaming and the cast fled the stage.”

“This is the world we live in,” he wrote. “This cannot be our world.”

Write to Mahita Gajanan at mahita.gajanan@time.com.