“Just tell me what I did real quick?” Mike asked “What was the gesture?”

“The gesture that you did,” Alves replied. “You did it to the line umpire and did it to me. You did with your racket like it was a gun. I don’t think that was appropriate.”

The $10,000 fine for Bryan, 41, was the largest men’s fine of this year’s U.S. Open so far. Gestures evoking guns have come under increased scrutiny during an epidemic of gun violence in the United States; there was yet another a mass shooting on Saturday in Texas.

“We thought it warranted that amount,” said Brendan McIntyre, a U.S. Tennis Association spokesman.

Mike Bryan, a six-time champion in men’s doubles at the Open, said in a statement: “I apologize for any offense I may have caused. We won the point and the gesture was meant to be playful. 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.”

The incident did not hurt the Bryans in the match; they broke Carballés in the game and won, 4-6, 7-5, 6-3. The match ended at 1:06 a.m. Sunday.