In the past two years, Brazilian Supreme Court Justice Teori Zavascki authorized the investigation of 47 politicians accused of corruption; he sanctioned the first arrest of a sitting congressman since Brazil’s dictatorship; and he suspended the mandate of house speaker Eduardo Cunha, accused of taking $40 million in bribes.

So when the twin-engine aircraft spiriting him to a holiday weekend outside Rio de Janeiro crashed last week, killing all aboard, suspicions were rife about the possibility of foul play.

The 68-year-old had been preparing to ratify an explosive body of testimony from 77 executives at construction firm Odebrecht, whose damning evidence in Operation Car Wash, Brazil’s $2 billion enquiry into bribes at state oil giant Petrobras, was expected to leave few politicians in Brasília untainted – including, perhaps, President Michel Temer.

The death has proven to be fertile ground for conspiracy theorists in a country in which a former president was reportedly assassinated in car accident by the military dictatorship in 1976 and a leading presidential candidate died in a similar light aircraft accident in 2014.

Prehn Zavascki, the son of the dead judge, noted that Zavascki and his family had received threats in recent months and said no possibility should be ruled out. “It is necessary to investigate thoroughly and to know if it was an accident or not,” he said in a radio interview. “The truth will come to the surface whatever it is.”

He said his father had been very focused on the Odebrecht testimony — nicknamed ‘The End of the World’ due to its potential impact on the country — and understood its importance. “He was perfectly aware of the impact this could have on the country and that this really could make the country clean,” he said.

Others joined calls for a swift investigation. “In virtue of the position of a Supreme Court justice in managing and deciding cases fundamental to national life,” Roberto de Figueiredo Caldas, the president of the Inter-American Court of Human Rights, said in a statement. “We expect an especially careful and rapid investigation into the circumstances of this disaster.”

The death of Zavascki is the latest twist in a tale of scandal that has traumatized Brazil. Operation Car Wash revealed institutionalized corruption on a vast scale, contributing to Brazil’s journey from a booming economy to record recession, and abetting the impeachment of President Dilma Rousseff in 2016.

Zavascki, who was appointed to the Supreme Court in 2012, took off in a Beechcraft King Air C90GT from São Paulo at about 1pm on Thursday. Also on board was pilot Osmar Rodrigues, the plane’s owner, hotel entrepreneur Carlos Alberto Fernandes Filgueiras, plus a masseuse who worked for Filgueiras and her mother.

All died when the plane crashed into the sea at 1.30pm just short of the airport in Paraty, a colonial town just outside Rio. There was rain, lightning and clouds over the town at the time. A boatman, Célio de Araújo, told local media that he saw smoke coming out of the left wing before the aircraft hit the water, but this could not be confirmed. Federal police and prosecutors are investigating alongside a military investigation team. A post-mortem examination found Zavascki had died of multiple head injuries.

Since 2015, Zavascki had been the Supreme Court judge overseeing the Car Wash case. The investigation is being run by a federal judge and prosecutors in the south of Brazil, but Zavascki gained a central role as only the country’s highest court can prosecute federal politicians, dozens of whom are under investigation. No major politician has yet been convicted — unlike Odebrecht chief executive Marcelo Odebrecht, who is currently serving a 19-year sentence.

Since December he had been working to ratify the Odebrecht plea bargains, which had been expected to happen by March. “This testimony was nicknamed ‘the end of the world’ in Brasília because Odebrecht allegedly had bribed many politicians of diverse parties who had yet to be involved in the Petrobras… scandal,” noted David Fleischer, a professor of politics at the University of Brasília.

The testimony of former Odebrecht executive Cláudio Melo Filho was leaked to the media, who revealed it contained 43 mentions of Michel Temer, Brazil’s president who took power after Rousseff’s impeachment. However, the reports did not elaborate on whether the testimony alleged wrongdoing.

The role of overseeing the Car Wash probe would ordinarily now fall to Zavascki’s replacement on the Supreme Court, who will be nominated by Temer. But it is possible the court’s president Carmen Lúcia will assign the case to other judges, if only to avoid further delays caused by a confirmation hearing in the senate.

In March, two of Temer’s allies, Romero Jucá and Sérgio Machado were recorded discussing a pact to try and stymie Operation Car Wash, including collusion with Supreme Court judges. But on the recordings Jucá said he had found that Zavascki was a “closed guy” and that he had not found a way to access or influence him.

Federal judge Sergio Moro, who has gained prominence by leading Operation Car Wash, said in a statement: “Teori Zavascki was a great judge and a Brazilian hero … Without him, there would be no Operation Car Wash. I hope that his legacy, of calmness, seriousness and firmness in enforcing the law, irrespective of the interests of those involved, even the powerful, will not be forgotten.”

Contact us at editors@time.com.

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