Serbia's ambassador to NATO was chatting and joking with colleagues in a parking garage at Brussels Airport when he suddenly 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 regular business, picking up an arriving delegation of six Serbian officials who were due to hold talks with NATO, the alliance that went to war with his country just 13 years ago.
A former author and activist opposed to the authoritarian regime of Serbia's former strongman Slobodan Milosevic, he was a respected diplomat and leading intellectual, officials said.
The diplomats, who spoke on condition of anonymity because they were not authorized to release details, said they knew of no circumstances, private or professional, that would have prompted him to take his own life.
One of the diplomats described the death to The Associated Press, saying she had spoken to a member of the delegation who had witnessed the leap from the 8- to 10-metre-high (26- to 33-foot-high) platform.
Speaking in Brussels, Serbia's Prime Minister Ivica Dacic said that "Belgian police are investigating, but it's obviously a suicide. It's hard to figure out the motives or causes."
The death cast a pall on the second day of a meeting of NATO foreign ministers. Officials said they were shocked by the news of the death of a very popular and well-liked ambassador.
"NATO's Secretary General Anders Fogh Rasmussen said he was deeply saddened by the tragic death of the Serbian ambassador," alliance spokeswoman Carmen Romero said. "Milinkovic was a highly respected representative of his country and will be missed at NATO headquarters."
Milinkovic is survived by his wife and 17-year-old son.