The Chinese doctor who first sounded the alarm about the coronavirus died Thursday from the disease, his friends and colleagues said.

Li Wenliang, 34, was an ophthalmologist at Wuhan Central Hospital. Wenliang was arrested on January 1, after attempting to share information on the coronavirus. It was well before Chinese health authorities revealed its full threat. Two days prior to his arrest, Li attempted to warn his medical school colleagues about the existence of a contagious new virus that resembled the lethal severe acute respiratory syndrome (SARS).

Li’s message began to spread across China, but his posts were censored by the government and he was detained for “rumor-mongering.” Instead of listening to his warnings, Chinese Communist authorities arrested him and forced him to write a “self-criticism,” a method of punishing dissenting voices.

The Washington Post reports that after arresting Li, Wuhan police went on Chinese state television to warn the public to not spread rumors. In conjunction with state media, they urged Internet users across the country to not believe online rumors and help build a “clear and bright cyberspace.”