[4] Due to his nationality and prominence in the UN hierarchy, Costa had been compared to Sérgio Vieira de Mello, who was also killed during a peacekeeping mission in Iraq along with 20 other members of his staff in August 2003.
At United Nations headquarters in New York City, his work included jobs in the Office of Human Resources Management and what was then the Department of Conference Services.
From 1992 to 2000, he was Chief of Personnel Management and Support Service, Field Administration and Logistics Division, Department of Peacekeeping Operations (DPKO), also in New York City.
[1][5] Costa was appointed Principal Deputy Special Representative for the United Nations Stabilization Mission in Haiti (MINUSTAH) from 15 November 2006.
[5] At the time, there were disagreements between Edmond Mulet from Guatemala, head of the mission, and Brazilian General José Elito, the MINUSTAH military commander.