A former GW student poses the greatest terror threat to the United States, a leading national security expert said during a congressional hearing Wednesday.

Anwar al-Awlaki, a radical Islamic terrorist who attended the Graduate School of Education and Human Development in 2001, is the biggest threat to the nation’s security, National Counterterrorism Center Director Michael Leiter said.

Leiter told the House of Representatives Committee on Homeland Security that al-Awlaki, a dual U.S.-Yemeni citizen and leader of al-Qaeda in the Arabian Peninsula, is a cause of concern due to his familiarity with the West.

Al-Awlaki is linked to the 9/11 hijackers and the Fort Hood shooting, and is believed to have a hand in planning the failed underwear bombing of Northwest Airlines Flight 253.

Times Square bombing suspect Faisal Shahzad told investigators in May al-Awlaki was an inspiration.

Al-Awlaki is also a threat because he encourages homegrown extremists – those with longstanding ties to the U.S. – to join terrorist organizations overseas, Leiter said.

“There are several others who we’re concerned with, but I think [al]-Awlaki probably does have the greatest audience on the Internet and the likes,” Leiter said. “In that sense, he’s the most important.”

Born in New Mexico, al-Awlaki, 39, lived in Yemen for a portion of his childhood before returning to the U.S. to further his education.

While at GW as a part-time doctoral student, al-Awlaki served as an assistant to a Muslim chaplain who was a member of the now defunct Interfaith Board of Chaplains.

After the 9/11 attacks, al-Awlaki fled to Yemen, later developing a connection with Major Nidal Malik Hasan, an army psychiatrist responsible for shooting and killing 13 fellow soldiers at the Fort Hood military base in Texas in November 2009.