BRUSSELS — Serbia’s ambassador to NATO was chatting and joking with colleagues in a multistory parking garage at Brussels Airport when he strolled to a barrier, climbed over, and flung himself to the ground below, a diplomat said.
By the time his shocked colleagues reached him, Branislav Milinkovic was dead.
His motives are a mystery. Three diplomats who knew Milinkovic said he did not appear distraught in the hours leading up to his death Tuesday night. He seemed to be going about his business, they said, picking up a delegation of six Serbian officials who were to hold talks with NATO, the alliance that went to war with his country just 13 years ago.
Belgian authorities confirmed that the ambassador had killed himself.
‘‘It was indeed a suicide,’’ said Ine Van Wymersch of the Brussels prosecutor’s office. She said no further investigation was planned.
A former author and activist opposed to the authoritarian regime of former strongman Slobodan Milosevic, Milinkovic was outgoing, had a warm sense of humor, and worked to keep good ties with ambassadors from other former Yugoslav countries, according to diplomats and acquaintances.
The diplomats said they knew of no circumstances — private or professional — that would have prompted him to take his own life.
But Milinkovic, 52, had mentioned to colleagues that he was unhappy about living apart from his wife, a Serbian diplomat based in Vienna, and their 17-year-old son.
One of the diplomats said she had spoken to a member of the delegation who had witnessed the leap from the 26- to 33-foot-high platform.
The diplomats all spoke on condition of anonymity.
The death cast a pall on the second day of a meeting of NATO foreign ministers.
NATO’s Secretary General Anders Fogh Rasmussen said he was ‘‘deeply saddened by the tragic death of the Serbian ambassador.’’
‘‘As Serbian ambassador to NATO he earned the respect and admiration of his fellow ambassadors,’’ he said.
When Yugoslavia was a united country, Milinkovic worked for a prominent Yugoslav foreign policy think-tank. But when Milosevic seized power in Serbia in late 1980s, Milinkovic joined other liberals who opposed the regime and presented a rare voice of moderation during the era when much of Serbia was engulfed in nationalist fervor. He established ties with human rights and other groups and remained active in antiwar groups.
After Milosevic was ousted in 2000, Milinkovic was appointed Serbia’s ambassador to the Organization for Security and Co-Operation in Europe, or OSCE, in Vienna.
He was transferred to NATO as Serbia’s special representative in 2004.
Milinkovic worked to foster closer ties with the representatives of Bosnia, Croatia, Macedonia, Montenegro, and Slovenia.
He leaves his wife and son.