A YouTuber's announcement of a video games console giveaway sparked chaos and a major police response in the heart of New York City on Friday.
A crowd of roughly 2,000 converged at Union Square Park in anticipation of free PlayStation 5 devices from celebrity Twitch streamer Kai Cenat.
Police said the influencer was among a number of people detained and he could be charged with inciting a riot.
People were seen hurling fireworks, bottles and toppling barricades.
Subway trains passed the Union Square stop during the incident, the BBC's US partner CBS reported, as police urged people to avoid the area.
People first gathered at around 13:00 local time (17:00 GMT) after Mr Cenat posted on social media - where he has more than 10 million followers and subscribers - that he would be handing out 300 PlayStations.
By 15:00, hundreds had piled on to streets surrounding one of New York City's busiest train stops.
They climbed cars and the train station entrance's roof and threw bottles at responding police officers.
New York Police Department declared a "level four" mobilisation, meaning roughly 1,000 officers were deployed to the scene.
During a livestream inside a vehicle near Union Square as the disorder was unfolding, Mr Cenat said: "They're throwing tear gas out there.
"We're not going to do nothing until it's safe. Everybody for themselves, because it's a war out there man."
Mr Cenat was taken into police custody at around 17:00. The crowd was finally dispersed about an hour later.
According to a CBS affiliate, Mr Cenat did not have a permit for the event, which was reportedly a collaboration with Bronx YouTube star Fanum.
NYPD Chief of Department Jeffrey Maddrey said: "We have encountered things like this before, but never to this level of dangerousness, where young people would not listen to our commands."
He added: "You had people walking around with shovels, axes, and other tools from the construction trade.
"In addition, individuals were also lighting fireworks. They were throwing them towards police, and they were throwing them at each other."
Mr Cenat made headlines in March after he broke the record for attracting the most Twitch subscribers by reaching 300,000.
Twitch is a livestreaming platform, where people typically play video games while chatting to viewers.
In the build-up to breaking the record, Mr Cenat launched a round-the-clock drive to boost his subscribers - chatting, gaming and interviewing guests, as well as sleeping, all on camera - for 30 days.