The FBI says Mostafa grew up in San Diego and, at some point, moved to Somalia and became a member of the al-Shabaab terrorist organization. A 2010 suicide bombing at a bar in Uganda during a World Cup soccer match killed a USA citizen working for a San Diego nonprofit. 'The FBI has not forgotten, has not stopped working, and will not stop until Mostafa is found'.
He graduated from University of California, San Diego in 2005 and - according to an Federal Bureau of Investigation poster offering a $5 million reward for information leading to his arrest - joined al-Shabaab around 2006.
The group claimed responsibility for two September 30 attacks on US and European military targets in Somalia, including one by an estimated 25 fighters who were killed when they tried to storm the Belidogle military airstrip, which hosts Somali and USA forces.
He eventually joined al-Shabaab, which seeks to establish a society based on "its rigid interpretation" of Sharia law and has pledged allegiance to Al-Qaeda, federal prosecutors said.
A federal arrest warrant was issued for Mostafa on October 9, 2009, after the original indictment.
One woman who asked not to be identified, told NBCSanDiego said she knew Mostafa from the time he worked at the front desk of an auto shop on El Cajon Blvd. Not scary or aggressive, ' she said.
Mostafa's father, Abdul Halim Mostafa, died a year ago but was said to be a well-respected man among the local community.
Shortly before Mostafa departed the USA, he married a Somalian woman.
Mostafa - also known as "Ahmed Gurey", "Ahmed", "Anwar", "Abu Anwar al Muhajir", and "Abu Abdallah al Muhajir" - was formerly a resident of San Diego but is now believed to be in Somalia, according to San Diego special-agent-in-charge Scott Brunner. ABC News reports his leadership in the group has allegedly led to the injuries or deaths of hundreds of innocent people in Africa.
One of the group's deadliest attacks targeted the Westgate shopping mall in Kenya that killed 60 people in 2013.