A deadly chemical was in the container that a Croatian war criminal took a swig from shortly before dying, a Dutch prosecutor said Thursday, as an independent investigation into the dramatic death of Slobodan Praljak continued.

“There was a preliminary test of the substance in the container, and all I can say for now is that there was a chemical substance in that container that can cause death,” prosecutor Marilyn Fikenscher said in a telephone interview. She declined to elaborate on the exact nature of the substance.

Praljak, 72, stunned the International Criminal Tribunal for the former Yugoslavia on Wednesday when he gulped liquid from a small bottle seconds after a UN appeals judge had confirmed a 20-year sentence.

The former wartime commander of Bosnian Croat forces said in court that he had taken poison. He was rushed to a hospital in The Hague, where he died, tribunal spokesperson Nenad Golcevski said.

Former Bosnian war veteran drinks apparent poison at his criminal trial0:28

Fikenscher said an autopsy, including toxicological tests, will be carried out soon on Praljak’s body.

Croatian Prime Minister Andrej Plenkovic said Thursday that Praljak wanted to send a message to the UN court that the verdict against him was unjust. Plenkovic said the former general was “obviously shaken by the possibility he would be convicted” of war crimes for his actions during Bosnia’s 1992–95 war.

Netherlands War Crimes Croatia

Praljak, centre, enters the tribunal on Wednesday. His lawyer called for a doctor, saying her client had claimed to drink poison while his verdict was being read. He later died. (Robin van Lonkhuijsen/Associated Press)

Fikenscher said the Dutch investigation will look into how Praljak managed to take the small bottle of poison into the tribunal’s tightly guarded courtroom.

Praljak and five other former Bosnian Croatian officials were convicted as part of a criminal plan to carve out a Bosnian Croat mini-state inside Bosnia in the early 1990s. All had their guilty verdicts sustained by the UN’s war crimes court Wednesday. Praljak’s conviction was in 2013.

Croatian Prime Minister Andrej Plenkovic offered condolences to Praljak’s family. Praljak’s actions reflected the “deep moral injustice” done to the six Bosnian Croats, the prime minister said.

Croatian state TV reported that President Kolinda Grabar Kitarovic cut short an official visit to Iceland and the government held an emergency session.

Mourning among Bosnian Croatians

Hundreds of Bosnian Croats have been lighting candles in public squares in cities around the country in honour of Praljak.

Praljak’s photos were plastered in Croat-dominated cities around Bosnia on Thursday where police presence was increased to prevent incidents.

APTOPIX Bosnia Slobodan Praljak Reax

Bosnian Croats gathered to light candles and pray for Praljak, in the southern Bosnian town of Mostar, 140 km south of Sarajevo, on Wednesday. (Amel Emric/Associated Press)

“Praljak was a legend for us. … He will live forever in our hearts,” said Ivica Gavric, who was a member of the Bosnian Croat forces during the war.

Meanwhile, the European Union has called on the Balkan leaders to respect the rulings of the UN war crimes court and work to achieve reconciliation and good relations.

“Delivering justice and fighting impunity are fundamental principles,” the EU delegation in Bosnia said in a statement Thursday.