A man wearing a T-shirt with a slogan protesting the use of private jets in the United Kingdom interrupted a match at the Laver Cup tennis exhibition at the O2 Arena in London by lighting his right arm on fire while sitting on the court.

The incident occurred during a break in a match between Stefanos Tsitsipas and Diego Schwartzman.

A man has set his arm on fire after invading the court at the Laver Cup on Roger Federer's last day as a professional tennis player. pic.twitter.com/g0LcBU8PeJ

The man, whose shirt read “end UK private jets,” doused the flames on his arm himself and was quickly removed by security, who also put out the small fire the protester set on the court using some sort of flammable liquid. Stuart Fraser of the Times reports that he later saw the man lying on the ground in a backstage area.

The match resumed after the protester was removed and the liquid was cleaned up. Per Sky Sports’ Anthony Joseph, the man was arrested on suspicion of aggravated trespass by Metropolitan Police and was taken to a hospital as a precaution.

“It came out of nowhere. I have no idea what this is all about. I never had an incident like this happen on court. I hope he is all right,” Tsitsipas said. “I wanted to proceed the match without having any minor changes to the court and to make sure it was playable, especially that area. It also got in my way of viewing experience, the way I saw the court later. There was a big mark over there and I just wanted to get it cleared up.”

The Laver Cup is a men’s team tournament pitting a team of European players against players from the rest of the world. This year’s event is particularly momentous because it marks the final competitive tournament for 20-time Grand Slam singles winner Roger Federer, who is retiring.

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Federer, who was sitting courtside when the incident took place, will take the court with fellow legend Rafael Nadal in a doubles match — the last of his career — that will begin Friday around 3:20 p.m. Eastern.

Earlier this year, a woman chained herself to the net during a French Open match between Casper Ruud and Marin Cilic in Paris. The woman was wearing a T-shirt with the message “we have 1028 days left,” a reference to a U.N. report that said humanity risked catastrophe unless it worked to halt climate change.

The use of private jets has come under fire because of the sizable carbon footprint they leave behind.