A fan ran on the court during game 4 of the Philadelphia 76ers - Washington Wizards series. The fan ran across the court, jumped to touch the backboard and was then tackled by security. Action stopped as security dragged him off the court and down the tunnel to be arrested.
Here's another angle where you can see he runs out to jump up and touch the backboard. That's when security shows up with the form tackle.
The fan pumped his fist as he was taken out of the arena.
Fans have become an increasing problem over the last few days. This is... the fifth fan incident of the NBA postseason. In just about a week Ja Morant's family was subjected to racist and sexually explicit remarks in Utah, Trae Young was spit on in New York, popcorn was thrown at Russell Westbrookin Philadelphia and a water bottle was thrown at Kyrie Irving in Boston.