The annual Global Citizen Festival in Central Park was transformed into a chaotic free-for-fall over the weekend, after a loud noise resembling gunfire sparked a panicked stampede in the crowd of tens of thousands.

Fifteen people suffered minor injuries in the commotion, which organizers now say was caused by someone "stepping on and popping a drink bottle." But widespread confusion and minimal communication in the moment led some in the crowd to believe an attack was underway. "Everyone thought there was a shooting or terrorist attack," one witness tweeted. "Not sure what happened but thousands of people running away from global citizen fest," said another.

Authorities—along with Coldplay's Chris Martin—quickly rushed the stage to explain the misunderstanding, at first blaming the noise on a collapsed police barrier. "Nobody is trying to hurt anybody, and you’re all safe, OK?" Martin reportedly told the crowd.

Within a few minutes, Cynthia Erivo took the stage and began singing "Bridge Over Troubled Water," and Janet Jackson taking the stage soon after. But some were not able to re-enter the Great Lawn following the panic.

"Unfortunately, while every effort was made to quickly re-open the gates, we regret some attendees were unable to re-enter the Park, and for that we apologize," Hugh Evans, the festival's CEO, said in a statement afterward. He also encouraged people who'd lost their personal property to visit the lost & found at the NYPD's Central Park Precinct—which reportedly resembled a "flea market" on Sunday.

Now in its seventh year, the festival aims to raise money to eradicate global poverty. Headliners this year included Janelle Monáe, Shawn Mendes, John Legend and Cardi B, who introduced her set with a video message from Michelle Obama. The musical performances were punctuated by speeches from leaders ranging from Governor Andrew Cuomo to Mark Ruffalo to Olympic skier Gus Kenworthy.

Republican Senator Jeff Flake also appeared on stage at one point, and urged the crowd to "join me in an elevator any time"—an apparent reference to the sexual assault survivors who confronted him after he announced that he planned to vote yes on Brett Kavanaugh's Supreme Court confirmation, but before he called for an FBI investigation into the nominee.

The strange, tumultuous event was ultimately closed out by The Weeknd, who performed a shortened set due to Central Park's curfew. The rapper later lamented the "mishap" on Twitter. "It was terrifying and they handled this terribly," responded one disappointed attendee.