On this day in 1993, at 12:18 p.m., a 1,200 pound terrorist bomb exploded in a parking garage of the World Trade Center in New York City. The explosion left a 60 foot-wide crater and caused several steel-reinforced concrete floors to collapse. The main structure of the skyscrapers was not damaged.

Lives Lost. Six people were killed by the blast, and more than 1,000 were injured. The building suffered more than $500 million in damage.

Evacuations. After the attack, 50,000 people were evacuated from the buildings; hundreds were suffering from smoke inhalation. The evacuation took the entire afternoon.

Manhunt. City authorities and the Federal Bureau of Investigation (FBI) launched a massive manhunt for suspects. Within days, a number of radical Islamic fundamentalists were arrested: Mohammed Salameh, a Palestinian, was arrested when he tried to get back his $400 deposit on the Ryder rental van used in the attack.

Ahmad Ajaj and Nidal Ayyad, who helped build the bomb, were arrested shortly after that.

Mahmoud Abouhalima, who was responsible for buying and mixing the explosives, fled to Saudi Arabia. He was caught in Egypt two weeks later.

Mastermind. The person who planned the attack ~ Ramzi Ahmed Yousef ~ remained at large until February 1995. He was finally arrested in Pakistan. Before traveling to Pakistan, he stayed in the Philippines. Terrorist plans ~ including a plot to kill Pope John Paul II and a plan to bomb 15 American airliners in 48 hours ~ were found in a computer he left behind. On his flight back to the United States, Yousef allegedly admitted to a Secret Service agent that he had directed the Trade Center attack from the beginning. Yousef claimed to have set the fuse that exploded the bomb. His only regret was that the 110-story Tower 1 did not collapse into Tower 2.

Driver. The same year Eyad Ismoil, who drove the Ryder van into the parking garage, was captured in Jordan and taken back to New York.

Tried and Convicted. In March of 1996, Salameh, Ajaj, Ayyad, and Abouhalima were convicted by a federal jury for their role in the bombing. Each was sentenced to life in prison.

New Jersey? All the men implicated had ties to Sheik Omar Abdel Rahman, a radical Egyptian religious leader who operated out of Jersey City, New Jersey, just across the Hudson River from Manhattan. In 1995, Rahman and 10 followers were convicted of conspiring to blow up the United Nations headquarters and other New York landmarks. Though prosecutors argued that the World Trade Center attack was part of the same conspiracy, there was little evidence to support the charge.

More Convictions, More Irony. In November 1997, Yousef and Ismoil were convicted only a few blocks away from the twin towers. They were both sentenced to life in prison without possibility of parole.

At Large. The only other man believed to be involved in the attack ~ Iraqi Abdul Rahman Yasin ~ remained at large.

Bin Laden? After the 1998 bombings of US embassies in Kenya and Tanzania, investigators began to suspect that Yousef had ties to Osama bin Laden, Saudi exile and the head of the anti-US al Qaeda terrorist network. Whether bin Laden was in fact involved in the 1993 twin tower attacks was never proved.

September 11. On September 11, 2001, two groups of al Qaeda terrorists finished the job Yousef began when they crashed two hijacked airliners into the north and south towers of the World Trade Center. The buildings' steel structures could not withstand the heat generated by the burning jet fuel. Both collapsed within hours of being struck.