US relations with the new Libyan government were thrust into the spotlight on September 11, 2012 when gunmen attacked and firebombed the US liaison office/mission in Benghazi, killing 4 Americans including Ambassador J. Christopher Stevens. Libya's interim leader Mohammed Magarief quickly condemned the attack and apologised to the US, describing it as "cowardly" and pledging to bring the killers to justice. Demonstrations denouncing the attack and supporting the United States were held in Benghazi the next day, with protesters mourning Stevens and signs declaring him 'a friend to all Libyans'. Libya cooperated with the US to investigate the attack, closing Benghazi's airspace for several hours to allow US drone patrols over the city on September 14.