Police in Beijing arrested an 81-year-old writer and publisher on vague charges of ‘causing trouble,’ news outlets including the South China Morning Post reported.

Huang Zerong, better known as Tie Liu, was taken from his home along with his caregiver Sept. 14. Police also confiscated four laptops, a tablet, a cell phone and some books and periodicals.

Zerong’s dog, named Mao Mao after former Chinese leader Mao Zedong, had been poisoned one day before his arrest. His wife also said Zerong had recently received threatening messages, the New York Times reported.

The arrest may be connected to a recent essay Zerong had written about the former head of the government’s propaganda department, Liu Yunshan, and restrictions placed on the press during Yunshan’s tenure, Reporters Without Borders said.

Zerong had previously spent 20 years in Chinese “re-education camps” for his criticisms of Mao and the China’s ruling Communist Party.