The Chinese Communist Party (CCP) is upset with the U.S.'s Department of Justice (DOJ) seeking prosecutions of several Chinese research scientists arrested in the U.S. this year. So upset that it's threatening to take Americans in China 'Hostage' if DOJ doesn't drop its prosecutions.
The reason that DOJ is pursuing their charges, is that the Chinese Researchers are affiliated with and working on behalf of the CCP's military wing the People's Liberation Army (PLA). These Chinese Researchers lied about their affiliations and their active duty status with the PLA in their applications to enter and work in the U.S.
VISA fraud, and lying to U.S. Immigration Authorities are not things not be taken lightly.
The CCP is playing a very dangerous game.