The British Daily Telegraph on Sunday revealed that Nidal Malik Hassan, the Arab psychiatrist who opened fire on soldiers at the Fort Hood U.S. Army Base last week, used to attend the same mosque as two of the terrorists who carried out the 9/11 attacks on the U.S. According to the report, the imam of the mosque is a well-known supporter of terrorist groups, and would often preach his support for their attacks.

FBI agents are working to determine if Hassan, who was in the U.S. Army for the past ten years before killing 13 people last week, personally knew the terrorists. The U.S. born Hassan is from a family that emigrated from an Arab village in Samaria.