The former in-house censor of China’s leading liberal newspaper Southern Weekly died on Wednesday - just three days into his retirement. Zeng Li had become a prominent figure during the weekly's protest against censorship in January. His farewell letter has been shared on Weibo thousands of times on Thursday and caused widespread soul-searching about the state of the media in China. “Looking back on the last four years, I made mistakes," Zeng wrote in his farewell letter, dated March 28. "I have killed some drafts that I shouldn’t have killed, I have deleted some content that I shouldn’t have deleted, but in the end I woke up, I would rather not carry out my political mission than go against my conscience, I don’t want be a sinner against history.” In January, Southern Weekly with its long tradition of liberal journalism had been caught up in the most vociferous protest against censorship by Chinese newsmakers in recent Chinese history. For three days, the weekly's staff protested outside their Guangzhou offices against the traditional new year's editorial having been replaced by provincial censors without consulting the editors. Thousands expressed their support online. An in-house censor's job is to make sure articles published by a newspaper do not go against provincial and central government censorship regulations. Zeng wrote in his blog in January that his job was to help the paper avoid political risks. In his farewell letter, Zeng wrote that he did not regret openly supporting the journalists in their protest against censorship. “In the Southern Weekly new year’s editorial incident, I stood up and spoke up out of sense of justice," he wrote. "I have a clear conscience, no regrets.” The farewell letter was shared by Chen Zhaohua, the editor of Southern Metropolis Weekly , another Southern Media Group publication. Even though Zeng's death was a private matter, the outpouring of grief reflected the shared values he stood for, Chen wrote. "This letter is surely an important document in China's history," Ma Yong, sociologist and history scholar at the Academy of Social Sciences wrote after Zeng's passing. "He used to be an in-house censor for Southern Weekly , he was entangled, but justice always dominated his mind," wrote Li Chengpeng , a prominent writer. "When this thing happened some time ago, he behaved beautifully. Now that he's gone, he will continue to edit this country in heaven." "He showed the strength of character and dauntlessness typical of a Southern Weekly newsman," wrote Qian Gang , a former managing editor of the newspaper and now a scholar at the University of Hong Kong. "Everyone has a choice."