Some people were arrested in clashes with law enforcement officers and other rowdy behavior, police said.
abcnews.com
21 arrests made in clashes with New York police after Knicks NBA Finals loss
Some fans
allegedly... 
threw beer bottles at or punched police officers.
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After the game, in which the Spurs broke the Knicks' 13-game playoff winning streak, fans spilled out of a watch party in Manhattan's Bryant Park and onto 42nd Street, where some allegedly turned violent.
The NYPD said that in the immediate aftermath of the game, several people allegedly threw beer bottles at or punched police officers, climbed on light poles and scaffolding, got into fistfights, and jumped on top of cars and taxi cabs.
Eight people were arrested on charges of assaulting police officers, criminal possession of a weapon, menacing, resisting arrest, and obstructing governmental administration, according to the NYPD. Thirteen others were issued criminal court summonses for disorderly conduct, the NYPD said.
Videos shared on social media showed some fans clashing with police officers, and other videos captured apparent Knicks fans attacking San Antonio fans on the streets, ripping off their Spurs jerseys.
One video showed NYPD officers wearing riot helmets escorting several people wearing Spurs jerseys to a taxi cab to protect them from a crowd yelling at them.
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Victor Wembanyama, other NBA Finals players condemn violence after Spurs fans attacked following Game 3: 'It's unacceptable'
Both the New York Knicks and the San Antonio Spurs shot below 30% from the field in the final frame of the Spurs' redemptive 115-111 victory in Game 3 of the NBA Finals at Madison Square Garden on Monday night.
The fourth quarter was a rock fight. What happened afterward in the streets of New York was much uglier.
Real fighting took place, as Spurs fans were attacked by New Yorkers in the aftermath of the Knicks squandering an opportunity to go up 3-0 in the series. People wearing Spurs gear were jumped and followed. Videos of postgame fracases in the streets went viral, including one in which a fan's Victor Wembanyama jersey was torn, taken and stomped on.
Here is another assault caught on camera:
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Just sayin': This is totally unacceptable.