Democratic Republic of Congo’s justice ministry said it had launched a murder investigation after an autopsy found the judge overseeing a landmark corruption trial of the president’s chief of staff had died from violent blows to the head.

Raphael Yanyi, who was presiding over the trial of Vital Kamerhe, once a close strategic ally of President Felix Tshisekedi, died on May 26 from what police at first reported was a heart attack.

An autopsy has since shown “he died a violent death, due to the blows of sharp points or knife-like objects, which were thrust into his head,” Justice Minister Celestin Tunda Ya Kasende told Reuters.

Yanyi’s body also showed signs of “toxic substances in non-lethal doses,” the justice ministry said in a separate statement announcing the launch of an investigation into the death.

It is the latest dramatic twist in a case that has gripped the Central African nation. Kamerhe, a top power-broker in Congolese politics for decades, is the most high-profile politician to have ever faced graft charges.

After his death, Yanyi was replaced at the head of the three-judge tribunal and Kamerhe’s trial has continued.