A crowd of thousands that packed Manhattan's Union Square in New York City for a popular livestreamer's hyped giveaway got out of hand.
Some in the crowd were clambering on vehicles, hurling chairs and throwing punches, leaving police struggling to rein in the chaos.
Aerial TV news footage showed a surging, tightly packed crowd running through the streets, scaling structures in the park and snarling traffic.
Shouting teenagers swung objects at car windows, and some people climbed on top of a moving vehicle, falling off as it sped away.
Others pounded on or climbed atop city buses.
Authorities forced to step in
By the evening, police officers in growing numbers had regained control of much of the area, but small skirmishes were still breaking out.
Young people were seen knocking over barricades, tossing bottles and even a flower pot at officers.
Police were seen wrestling people to the ground and chasing them down the street.
There were some arrests and some injuries, including to officers, NYPD Chief of Department Jeffrey Maddrey said.
"People were suffering out here," Mr Maddrey said, adding that he saw people bleeding and having asthma and panic attacks.
"Individuals in the park began to commit acts of violence towards the police and the public," he said at a press conference.
"Our officers were attacked. We were crushed, we were pushed."
Some people set off fireworks, while others wielded tools from a construction site, Mr Maddrey said.
It was not immediately clear what had sparked the chaos.
Police formed lines in the street to try to direct the crowd.
Gaming products announced for giveaway
On his Instagram feed, the streamer Kai Cenat had an image promoting a giveaway in the park.
Some young people leaving the park said they had come expecting to get a computer for live streaming and a new PlayStation.
Skylark Jones, aged 19, and a friend came to see Cenat and try to get something from his giveaway, which they said was promoted as a chance for things like gaming consoles or a gaming chair, as well as an opportunity to see the popular streamer.
When they arrived the scene was already packed, bottles were being thrown by people in the crowd and there was a commotion even before Cenat appeared, they said.
"It was a movie," Jones said. Police "came with riot shields, charging at people."
Livestreamer has millions of online followers
Cenat, aged 21, is a video creator with 6.5 million followers on the platform Twitch, where he regularly livestreams.
He also boasts four million subscribers on YouTube, where he posts daily life and comedy vlogs ranging from "Fake Hibachi Chef Prank!" to his most recent video, "I Rented Us Girlfriends In Japan!"
His 299 YouTube videos have amassed more than 276 million views among them.
In December, Cenat was crowned "Streamer of the Year" at the 12th annual Streamy Awards.
Messages sent to his publicist, management company and an email address for business inquiries were not immediately returned.
Livestreaming on Twitch from a vehicle as the event gathered steam, Cenat displayed gift cards he planned to give away.
Noting the crowd and police presence, he urged, "Everybody who's out there, make sure y'all safe. … We're not gonna do nothin' until it's safe."
Eventually he and an entourage got out of the vehicle and hustled through an excited crowd, crossed a street and went into the park before the stream cut out.
'It's never like this'
Carina Treile, manager of Petite Optique, an eyeglass shop nearby, was forced to remain in her store after it closed because police were still clearing the scene outside.
Ms Treile said, "Usually with people giving away free stuff, it's never like this. It's very organized,"
"And here we have a very chaotic scene."
Ms Treile said there were some loud bangs at some point, which frightened some in the crowd.
"That was a little bit scary, especially when people started running."
Police, some with batons, used metal barricades to push the crowd back and loudspeakers to issue a warning: "This gathering is unlawful. You are ordered to disperse."
AP/Reuters/ABC
