New York - American doubles player Mike Bryan was fined $10 000 (R152 000) by the US Open on Sunday for his using racquet his to make a shooting gesture at a line judge.
Bryan, playing alongside twin brother Bob, held his racquet upside down and pointed it towards the official after successfully challenging an incorrect call.
Chair umpire Mariana Alves issued a code violation against Mike Bryan for unsportsmanlike conduct.
The Bryan brothers, winners of 16 Grand Slam doubles titles as a team, went on to win the second-round match 4-6, 7-5, 6-3 against Roberto Carballes Baena of Spain and Argentina's Federico Delbonis.
It is the highest fine received by a male player so far at this year's tournament.
"I apologise for any offense I may have caused. We won the point and the gesture was meant to be playful," Bryan said in a statement cited by the New York Times.
"But given the recent news and political climate I understand how my gesture could be viewed as insensitive. I promise that I will never do anything like this again."
Seven people were killed in Texas on Saturday in the latest of several mass shootings to occur in the United States this year.