The New York Police Department says 30-year-old Julian Simpson and others went on an apartment building roof to look at the Empire State Building lights early Wednesday.
The building was lit in rainbow colors in recognition of a survey that found most Australians support marriage equality and ensured that lawmakers will vote on a same-sex marriage bill this year.
Simpson was an official with Australia's United Nations mission. Australia's Department of Foreign Affairs and Trade says it's assisting the diplomat's relatives, who are asking for privacy.
Australian Prime Minister Malcolm Turnbull says the death of Simpson, the second secretary to the United Nations for Australia, was a "shocking tragedy."
Here's a report from an Australian news network:
"Hearts go out to his family, but I cannot provide any more details," Turnbull told Australia's Seven Network television.
Police say Simpson swung a woman around and her husband got angry. The men then went on a seventh-floor apartment terrace, and Simpson offered to prove he was trustworthy by playing a so-called trust game.
Simpson went to the ledge and leaned back, Authorities say he grabbed for the other man's hand but slipped and fell to a second-floor landing.