Purges in communist states have rarely stopped with the execution of one senior Party member, especially when he has been tortured into "confessing" at his show trial that he was planning to stage a coup using "high-ranking military officers" and other close allies.
"I didn't fix the definite time for the coup," Jang Song Thaek, the former number two in the hierarchy of the world's last totalitarian state, said at his trial. "But it was my intention to concentrate (my allies in) my department and in all the economic organs in the Cabinet and become premier when the economy goes totally bankrupt and the state is on the verge of collapse."
It's most unlikely that Jang was really planning a coup, but all of his suspected allies and associates in his own department and other parts of the government, plus any senior military officers suspected of less than total loyalty to Supreme Leader Kim Jong Un, are in grave danger.