In Gorcher's book by Ivan IV Reddy.

It also provides the reason why Bobersky betrayed the czar. In his later years, Reddy was very afraid of dying suddenly without repentance and communication. So he summoned 60 wizards and witch doctors from all over the country to take strict care of them. The tsar sent Jilski to know and report to himself the divination and prophecy of these people every day. It is said that witches once told Besky. The most powerful star in the sky opposes the tsar. They even predicted the death date of the czar. But Besky didn't dare to report to the czar truthfully. Finally, the tsar knew. He said angrily: On this day, he will burn all astrologers, and Besky who concealed this prophecy will be beheaded. In this way, after the wizards predicted the death of the tsar, the threat to their own lives became a reality. This constitutes the murder of the Tsar by Beysky and Godunov.