The 1990s also featured a series of increasingly violent attacks associated with Islamist terrorists, including al-Qaeda, a radical Islamist militant organization led by Osama bin Laden. On February 26, 1993, a truck bomb was detonated at the World Trade Center in New York City, killing six civilians and injuring 919 others, 88 firefighters, and 35 police officers. The attack was intended to destroy the foundation of the North Tower, knocking the tower into the South Tower, which would destroy both buildings and kill thousands of people. While this did not happen, the bomb caused considerable damage to the lower levels of the North Tower. In 1994, four men were convicted of carrying out the bombing and in 1997, two men were convicted for their roles, including the truck driver and the mastermind, Ramzi Yousef.