(CNN) US tennis star Mike Bryan has been fined $10,000 for pretending to shoot an on-court line judge with his racket at the US Open Sunday.

The doubles player was initially handed a code violation for unsportsmanlike conduct by chair umpire Mariana Alves during his second-round win with brother Bob against Federico Delbonis and Roberto Carballés Baena.

Bryan had successfully challenged the line judge's decision after replays on the big screen showed the ball had landed narrowly behind the baseline.

After the call was corrected, Bryan mimicked a rifle with his racket and aimed it at the line judge in question.