Federal prosecutors in New York filed criminal charges against a Chinese dissident living in the U.S., accusing him of covertly working for China’s intelligence agency, the Ministry of State Security, and spying on pro-democracy activist groups, according to a criminal complaint obtained by CBS News.

Yuanjun Tang once protested against the Chinese Communist Party during the 1989 Tiananmen Square demonstrations, court documents said, and fled to Taiwan and the U.S. But prosecutors alleged decades later, he agreed to work for China’s intelligence agency in a bid to see his family living in mainland China.

Investigators said Tang first sought opportunities to visit his family in 2018 and was ultimately introduced to an unnamed intelligence officer. The two allegedly began communicating and the Chinese intelligence agent pushed Tang to collect “information about PRC Dissidents, pro-democracy events, and the political asylum process,” according to court documents.