The Navy captain, who was removed from his command of a coronavirus-stricken aircraft carrier, has tested positive for the COVID-19 virus.

Two Naval Academy classmates of Capt. Brett Crozier confirmed the diagnosis to the New York Times. Crozier started showing symptoms before his ouster on Thursday, the classmates said. It’s unclear when he was tested for the virus, and he’s being quarantined at Naval Base Guam.

Crozier was fired after the leak of a letter he sent to Navy leaders in which he pleaded for help in containing the virus as it spread throughout the U.S.S. Theodore Roosevelt.

Secretary of Defense Mark Esper said Sunday that there were 155 confirmed cases of the coronavirus among sailors aboard the aircraft carrier. He added that more than half of the ship had been tested, and there have not been any hospitalizations.

“The letter was sent over not-secure, unclassified email even though the ship possesses some of the most sophisticated equipment in the fleet,” Acting Navy Secretary Thomas Modly said Thursday. “It wasn’t just sent up the chain of command, it was copied to a broad array of other people.”

Videos shared on social media on Friday showed hundreds of sailors aboard the ship cheering for Crozier as he disembarked.