Tennis star Frances Tiafoe is apologizing after his outsized reaction to a loss in the Shanghai Masters tournament.

During his third round match against Roman Safiullin of Russia on Tuesday, Oct. 8, Tiafoe first argued with chair umpire Jimmy Pinoargote over a time violation call as he went to serve in the final-set tiebreak.

Tiafoe tried to say that he had already thrown the ball in the air, initiating the serve. “No, no, no, no, I tossed the ball up … I was ready to serve. Dude, that’s the rule,” he said, CNN reported.

But Pinoargote replied, “I’m not buying it, it’s the second serve,” and play continued, with Tiafoe losing the tiebreak, and therefore the match.

Tiafoe then unleashed on Pinoargote after the end-of-match handshake with Safiullin.

In video of the incident, Tiafoe can be heard saying to Pinoargote, “F— you, man. F— you. Seriously, man. F— you. You f—ed me in the f—ing match.”

Tiafoe continued with his outburst, telling the umpire “Three f—ing hours, and you’re gonna do that. Why? … You f—ed the match up. Great f—ing job. F— you. Three f—ing hours I’m out here battling, only for my livelihood.”

Never miss a story — sign up for PEOPLE’s free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from celebrity news to compelling human interest stories.

Later that evening, Tiafoe posted an apology on Instagram regarding his behavior.

“I really apologize for the way I acted tonight. That is not who I am and not how I ever want to treat people,” he posted on his Instagram Stories. “I let my frustration in the heat of the moment get the best of me and I’m extremely disappointed with how I handled the situation. That’s not acceptable behavior, and I want to apologize to the umpire, the tournament and the fans. I’ll be better for y’all,” he wrote.

As of now, there is no word on if Tiafoe will be penalized due to his behavior toward Pinoargote.

Heading into the Shanghai Masters, Tiafoe had put together a strong season. He’s currently ranked 17th in the world in the ATP standings and had his best-ever finish at the U.S. Open after making it to the semifinals.