North Korea reportedly executed its special envoy to the U.S. and four other Foreign Ministry officials after the February U.S.-North Korea summit in Hanoi didn’t work out.

According to Reuters, South Korean newspaper Chosun Ilbo reports that Kim Hyok Chol—who had served as U.S. special representative for North Korea Stephen Biegun’s counterpart in the run-up to the Hanoi summit—and the other officials were charged with spying and executed at Mirim Airport shortly after the summit.

Kim Yong Chol, Secretary of State Mike Pompeo’s counterpart prior to the summit, was reportedly subjected to “forced labor and ideological education” in Jagang Province. Negotiator Kim Song Hye, who worked with Kim Hyok Chol during the summit, and interpreter Shin Hye Yong are said to have been sent to a political prison camp—the latter for supposedly making a mistake while interpreting.

An anonymous South Korean official also told the newspaper that North Korean leader Kim Jong Un has made his sister, Kim Yo Jong, “lie low” after she aided him in the summit.

“We are not aware of Kim Yo Jong’s track record since the Hanoi meeting,” the official said. “We understand that Kim Jong Un has made her lie low.”

The executions are believed to be part of a purge orchestrated by Kim Jong Un to distract from “internal turmoil and discontent,” according to Chosun. Meanwhile, North Korean state newspaper Rodong Sinmun wrote Thursday that there were “traitors and turncoats” who had betrayed Kim Jong Un “according to the trend of the time.”

“Acting like one is revering the Leader in front (of others) but dreaming of something else when one turns around, is an anti-Party, anti-revolutionary act that has thrown away the moral fidelity toward the Leader, and such people will not avoid the stern judgment of the revolution,” the Rodong commentary read.