Ex-FSB operative Dmitry Dokuchayev was the last of four high-profile figures to receive treason sentences. All four were arrested in Russia in December 2016 shortly after the U.S. accused Russia of trying to influence its presidential election through hacking.

A former agent of Russia’s Federal Security Service (FSB) has been sentenced to six years in maximum-security prison on charges of treason in the agency’s worst scandal in recent history.

The Moscow Military District Court handed Dokuchayev a six-year sentence and stripped the major of his military rank after finding him guilty of treason, Interfax reported Wednesday.

His superior, ex-FSB security officer Sergei Mikhailov, and cybersecurity expert Ruslan Stoyanov were sentenced to 22 and 14 years respectively on the same charges in February.

Meduza reported that Dokuchayev received a lighter sentence after agreeing to a plea bargain and testifying against Mikhailov.

Source-based reporting has claimed that Mikhailov handed FSB secrets to Dokuchayev, who then gave them to Stoyanov — who then gave them to a U.S. cybercrime threat analyst.

The treason charges are linked to leaks to the U.S. on the Russian founder of the Chronopay payment system. Russian media reported in 2017 that the group was suspected of providing U.S. officials with information about Russian military intelligence hacking of the Democratic National Committee — though the allegation was never officially included in their charges.

Russian internet entrepreneur Georgy Fomchenkov — another suspected liaison between Mikhailov and the U.S. — was sentenced to seven years in prison for state treason in the interests of the United States last week.