A Dominican professional basketball player named Óscar Cabrera Adames has died of cardiac arrest at the age of 28, according to reports.

According to an Instagram post from Dominican sports journalist Héctor Gómez, Adames died while undergoing a stress test at a Santo Domingo health facility. Adames is believed to have suffered from myocarditis, a disease that erodes the heart’s ability to pump blood. Following his death, several social media posts written by Adames were found in which he said he developed myocarditis after receiving two coronavirus vaccine shots.

Adames says he agreed to receive the vaccine because it was a requirement for work.

“I got a damn Myocarditis from taking a fckng vaccine,” Cabrera wrote. “(I got 2 doses of Pfizer) And I knew it! Many people warned me.”