NAIROBI // The October Al Qaeda video shows a light-skinned man handing out food to families displaced by famine in Somalia. But the masked man is not Somali, or even African - he's a Wisconsin native who grew up in San Diego.
A handful of young Muslims from the US are taking high-visibility propaganda and operational roles inside an Al Qaeda-linked insurgent force in Somalia known as Al Shabab. While most are from Minnesota, which has the largest Somali population in the US, Al Shabab members include a Californian and an Alabaman with no ancestral ties to Somalia.
"They are being deployed in roles that appear to be shrewdly calculated to raise Al Shabab's international profile and to recruit others, especially those from the United States and other English-speaking countries," said Anders Folk, a former assistant US attorney who prosecuted suspected Al Shabab supporters in Minnesota.
Officials fear another terrorist attack in East Africa. Kenya announced on January 7 that it had thwarted attempted Al Shabab attacks over the holidays. The same day, Britain's Foreign Office urged Britons in Kenya to be extra vigilant, warning that terrorists there might be "in the final stages of planning attacks".
More than 40 people have travelled from the US to Somalia to join Al Shabab since 2007, and 15 of them have died, according to a report from the US House of Representatives homeland security committee. Federal investigations into Al Shabab recruitment in the US have centred on Minnesota, which has more than 32,000 Somalis.
At least 21 men have left Minnesota to join Al Shabab in that same time. The FBI has confirmed that at least two of them died in Somalia as suicide bombers. A US citizen is suspected in a third suicide bombing, and another is under investigation in connection with a fourth bombing on October 29 that killed 15 people.
The person featured in the Al Qaeda video was Jehad Mostafa, 30, a Californian who handed out food using the name Abu Abdullah Al Muhajir, according to the Site Monitoring Service. The Washington Post reported last year that Mr Mostafa served as top lieutenant to Saleh Nabhan, a senior Al Qaeda operative who would be killed by Navy Seals in a helicopter attack inside Somalia in 2010.
Mr Mostafa and the Alabaman, Omar Hammami, 27, are among about a dozen men who have been charged in federal court in the US and are believed to be in Somalia.
The Americans appear to have been motivated by the Ethiopian army's intervention in Somalia in 2006, which they saw as an invasion. However, many experts believe it is only a matter of time before Al Shabab turns its wrath on the US, which in February 2008 designated it as a terrorist organisation.
US military commanders fear that Americans inside Al Shabab could train as bombmakers and use their US passports to carry out attacks on their homeland.
EK Wilson, the agent overseeing the FBI's investigation in Minneapolis, said he cannot comment on whether there is an outstanding order to capture or kill Americans fighting for Al Shabab. The FBI has publicly said the Americans should return to the US.
It is a mystery what caused Mr Mostafa, a young man whom many remember as mild and friendly, to join an extremist group.
He grew up in San Diego and graduated from the University of California San Diego. The imam Abdeljalil Mezgouri of the Islamic Center of San Diego, the city's largest mosque, said Mr Mostafa was a respectful teenager and good student.
Mr Mezgouri said Mr Mostafa got married in his early 20s to a woman he believed was from Somalia.
"He was a very quiet, very loving boy. He didn't talk too much but when he did talk, people liked him," Mr Mezgouri said.
Public records show Mr Mostafa was the president of the now-defunct Muslim Youth Council of San Diego. The former organisation's website says the group is "dedicated to showing the world that Islam is a religion of peace and Muslims are a peaceful and productive part of society".
Mr Mostafa's father, Halim Mostafa, a Kurdish Syrian, is a prominent figure in San Diego's Muslim community who has tried to build bridges with non-Muslims. He made a low-budget film released in 2008 called Mozlym to show how the true meaning of Islam is often lost amid the misconceptions of non-Muslims in America, according to the film's website.
Mr Mostafa's father declined to be interviewed for this story.
"I just don't want to get involved. I'm really sorry I cannot say anything. God bless you," he said.
Edgar Hopida, a spokesman for the San Diego chapter of the Council on American-Islamic Relations, said Halim Mostafa believes in the most liberal interpretation of Islam and noted that "it's ironic if his son is involved with Al Shabab."
Mr Mostafa is believed to have met the American militant Anwar Al Awlaki about a decade ago at a San Diego mosque, according to The Washington Post. He went to Somalia in 2005. Federal officials declined to comment.
Mr Mostafa was indicted in August 2010 on terrorism charges for allegedly providing material support to Al Shabab. Mr Mostafa has a leadership role inside Al Shabab and serves as a key liaison to Al Qaeda, said Evan Kohlmann, who has assisted government investigations into Al Shabab recruiting and financing.
The Associated Press could not reach Mr Mostafa or Mr Hammami for comment. A spokesman for Al Shabab said questions that the AP emailed were "of a personal nature relating to the roles and activities of certain individuals and for that reason they were left unanswered".
The spokesman said Al Shabab and Al Qaeda were "brothers in Islam." He did not provide a name but emailed from an address used by Al Shabab's media outreach wing, which also recently launched a Twitter feed.
The Alabaman, Mr Hammami, 27, has taken on the role of jihadi lecturer and Islamic scholar. After US Navy Seals killed the Al Qaeda chief Osama bin Laden in Pakistan this year, Mr Hammami threatened to avenge the killing at a news conference near Mogadishu.
Al Awlaki's killing by a US drone in Yemen in September left Mr Hammami as the most influential US English speaker in the jihadi propaganda sphere, said the terrorism expert Ben Venzke.
"His more accessible image and manner of speaking may prove a growing and significant threat to not just the region around Somalia but for future attacks on US soil," said Mr Venzke of the Washington-based IntelCenter.
Rick Nelson, a senior fellow at the Center for Strategic and International Studies, said the possibility of military reprisal might not deter Al Shabab from carrying out an attack inside the United States.
"All the elements are there for it to happen," Mr Nelson said.