Simplify the following text for a Grade 13 native English-speaking person.
Original: The United Nations ( UN ) reported that the headquarters of the United Nations Stabilization Mission in Haiti ( MINUSTAH ) , located in the capital , had collapsed and that the Mission 's Chief , HÃ di Annabi , his deputy , and the acting police commissioner were confirmed dead .
Simplified: The headquarters of the United Nations Stabilization Mission in Haiti ( MINUSTAH ) , located in the capital , collapsed , killing many , including the Mission 's Chief , HÃ di Annabi .