Chinese human rights lawyer Li Baiguang was reported dead on Monday after checking in to the Number 81 People’s Liberation Army Hospital in Nanjing, despite friends saying the 49-year-old was previously in good health and complained only of a minor stomach ache.

“After a sudden outbreak of illness, the efforts to save him failed, and he passed away. He had not done a health check recently, so we do not know if there was a long-term cause,” an unnamed source with knowledge of the case told Reuters.

The hospital declined to comment on Li’s death, as did China’s public security ministry.

Li Baiguang received the 2008 Democracy Award for religious freedom from the National Endowment for Democracy for his work on behalf of persecuted Christian pastors in China. When presenting the award, Rep. Frank Wolf (R-VA) compared Li and his fellow honorees to Alexander Solzhenitsyn and Andrei Sakharov for the challenge they posed to China’s authoritarian rulers.

“The result of a lack of supervision and checks and balances within China’s one-party system is that China is lagging behind in advancing freedom, democracy, human rights, and rule of law,” Li said in his acceptance speech. “However, my experiences tell me, that using the law to protect citizens’ rights and freedom can play a role in restricting abuses of official authority and in empowering citizens in China.”

Bob Fu, a Chinese-American friend of Li’s, said his death was suspicious.

“Li did not drink alcohol and he did not smoke. For someone’s liver to fail overnight at the age of 49 is highly unbelievable,” said Fu.

“The hospital alleged that he had liver problems and that he bled to death, but Li was previously healthy,” Fu said in a statement released by his nonprofit group ChinaAid. “China has a history of either neglecting the medical conditions of human rights activists until they succumb to them, or declaring previously healthy people dead.”

Fu described Li as “one of China’s most courageous, pro-constitution lawyers” and said he was “treated violently last year and was threatened a number of times recently by the Chinese regime.”

ChinaAid clarified that Li was “kidnapped by Chinese officials in Zhejiang province, beaten, and forced to leave the area on the threat of dismemberment for defending farmers whose land was illegally taken by the government.” The group flatly accused the Chinese government of murdering him.

“Like in the sudden death of Dr. Liu Xiaobo, the Chinese regime should be held totally accountable. The whole world should demand that the Chinese government give a full, independent, and transparent account on what caused Dr. Li’s sudden death,” Fu urged.

Nobel Peace Prize-winning Liu Xiaobo died in July 2017 while in Chinese custody, leading to criticism that Beijing gave him substandard care and refused to allow foreign doctors to provide treatment that might have saved his life.

Li Baiguang leaves behind a wife and an eight-year-old son.