A 25-year-old professional video gamer has been forced to retire due to a thumb injury.

Thomas “ZooMaa” Paparatto announced he’s “taking a step back from competitive Call of Duty” on Twitter.

“This is the hardest thing I’ve ever had to write, I am stepping down and will no longer compete in competitive Call of Duty for the foreseeable future,” he said in a separate blog post.

“It breaks my heart to step away from a game I put my heart and soul into every single day for eight years,” he added. “Tearing up just writing this, but I don’t know what else to do at this point.”

Paparatto plays for an esports team called New York Subliners and he has earned $387,019 from 87 tournaments, according to Esports Earnings. His largest prize from a single tournament came in April 2018, when he won $53,125 in a Call of Duty: Cold War II competition.

The U.S. gamer struggled with weakness in his thumb and his wrist a few years ago while playing a game called FaZe Clan. He had to have surgery as a result.

“Going through that process of getting healthy again was one of the hardest things I ever had to do both physically and mentally, which led to a lot of stress and anxiety,” he said. “Unfortunately, the injury has returned making it really hard for me to compete at the highest level against some of the best players in the world.”

He said that playing through the pain in his hand “just isn’t possible anymore” and that he doesn’t enjoy competing when he can’t be the “ZooMaa everyone knows and loves.”

Fans and fellow gamers shared their support following his announcement. 

Many professional gamers train or compete for over 10 hours a day, and some of them rake in over a $1 million a year in the process. However, the physical and mental strain on the body can sometimes result in health problems.  

Sam Matthews, founder and chief executive of Fnatic, told CNBC in December: “These people are fit and healthy largely, but there’s always an anomaly to the rule.”