He is a German citizen, and was born to a Moroccan father and a German mother in 1975. The family moved to Morocco when he was nine years old. He came to Hamburg in 1995. He enrolled in an electrical engineering program at a technical university in 1996. He spent five months in the German army and then received a medical discharge.
On November 1, 1998, he moved into an apartment in Germany with future hijackers Mohamed Atta and Ramzi bin al-Shibh. He had already been under investigation by German intelligence for his connections with Mohammed Haydar Zammar, a radical Islamic cleric. Through this, German intelligence was able to learn some of the activities of Atta and others.
In October 1999, he got married at the Al-Quds Mosque in Hamburg. Atta, Jarrah, Shehhi, Zammar, and bin al-Shibh all attended his wedding.
He told his employer in June 2001 that he was going to an internship for a software company in Pakistan. His aunt, Barbara Arens, says that she was suspicious and that she went to the police and pleaded to them "to do something." She says that police took no action against him. Al-Qaeda leader Khalid Sheikh Mohammed told him in August that if he wanted to go to Afghanistan, he should go in the next few weeks, because it would soon become more difficult. He left Germany on September 4, 2001, just a week before the attacks, and flew to Karachi via Istanbul.
He is at large.