At least one GW alumnus died in Tuesday’s attacks. John P. O’Neill, 49, who received his master’s of forensic sciences from the Elliott School of International Affairs in 1978, was serving as head of security for the World Trade Center at the time of the attack, GW spokesman Eric Solomon said.

According to a Washington Post obituary, O’Neill died after he ran back into one of the burning buildings to help trapped workers.

O’Neill retired from his post as counter-terrorism chief at the New York office of the Federal Bureau of Investigation last month. He was under investigation last year for leaving a briefcase filled with classified documents unattended in Tampa, Fla., according to a Washington Post obituary. The briefcase was returned to another hotel after 90 minutes and officials did not think its contents were disturbed, according to an Aug. 21 Washington Post article.

In a 1997 speech to the National Strategy Forum, O’Neill cited the 1993 World Trade Center bombing as an example of international terrorism. O’Neill had investigated the embassy bombings in East Africa in 1998, the U.S.S. Cole attack in Yemen in 2000 and headed an operation gathering information about suspected terrorist Osama bin Laden, according to The Post.

Also unaccounted for is Andrew Stergiopoulos, 23, a 2000 graduate of the School of Business and Public Management. He worked on the 103rd floor of the World Trade Center north tower in the office of Cantor-Fitzgerald International, L.P., a global stock brokerage and investment firm.

Family members say they have not heard from Stergiopoulos since American Airlines flight 11, the first plane to hit, crashed into the north twin tower shortly after 9 a.m Tuesday. Stergiopoulos was on the GW men’s lacrosse team and earned his degree in finance. He is from Great Neck, N.Y.

– Drew Wiseman and Jason Safdie