Salah Osman Ahmed, another suspect in the case, pleaded guilty in July to providing material support to terrorists.
Families that belong to this Minnesota mosque, Abubakar As-Saddiqu, were suspected of having a role in their loved ones' disappearance.
One young man attended secret meetings in Minneapolis. Another got a phone call, urging him to leave Minnesota and go to Somalia to fight. Terrorist training videos featuring English speakers pepper YouTube, calling others to the cause.
Details are emerging about how terrorists in Somalia have lured young American men — including as many as 20 from Minnesota — back to their homeland to join their jihad. At least three have died, including one who authorities believe is the first American suicide bomber. Three others have pleaded guilty in the U.S. to terror-related charges.
Court proceedings and interviews with community members, attorneys and terror experts indicate the Somali-based terror group, al-Shabab, uses widespread recruitment tactics including a vast Web-based network.
"Al-Shabab 10 years ago would be a two-bit, paramilitary group that no one would've cared about ... sitting in a basement somewhere stockpiling rocket-propelled grenades and bullets for AK-47s," said Bruce Hoffman, a terrorism specialist at Georgetown University. "Now, we see them reaching into the United States."
Like many terror groups, al-Shabab uses Internet videos to draw disenfranchised young men into its fold. Many feature typical militant scenes: men with covered faces firing automatic weapons, marching or practicing martial arts. Some show close-up footage of dead bodies and religious documents.
But al-Shabab's propaganda sets it apart.
"I would say they were among the most explicit, the most violent, and the most enthusiastic videos of any jihadi organization out there," said Evan Kohlmann, a terror consultant.
The group, which the U.S. government says has ties to Al Qaeda, also uniquely targets Americans and English speakers, Kohlmann said.
Some videos show English-speaking suicide bombers reciting last wills. Others showcase a man with shoulder-length brown hair who calls himself Abu Mansour the American commanding fighters and glorifying jihadists killed in Somalia.
Al-Shabab's online propaganda proliferated in recent years after messages from Osama bin Laden appeared on jihadist forums encouraging followers to go to Somalia. The country of 7 million has not had a functioning government since 1991.
Earlier this month, U.S. Secretary of State Hillary Rodham Clinton said Washington was concerned al-Shabab uses foreign fighters and there was no doubt the group wants to take control of Somalia and "launch attacks against countries far and near."
Experts say Western recruits' passports and cultural awareness make them valuable.
"You can't take someone from the slums of Mogadishu and take them on some suicide mission to Rome, Paris, New York," Hoffman said. American deaths also bring more attention to al-Shabab's cause, he said.
In Minneapolis, home to the largest population of Somali immigrants in the U.S., a federal investigation into the missing men is illuminating the recruiting.
Salah Osman Ahmed, 26, of New Brighton, told a judge last month that he attended "secret meetings" in Minneapolis starting in October 2007. There, he said, a group of "guys" talked about returning to Somalia to fight Ethiopians. At the time, the Ethiopian army, which many Somalis viewed as abusive, occupied parts of Somalia.
When Ahmed got to Somalia, his attorney said, he realized what al-Shabab really was.
Hoffman said the underground meetings fit a pattern.
"The conspiratorial air is part of this group bonding," Hoffman said. "That kind of atmosphere makes these young men think that what they are doing is all the more important."
Hoffman also said terror groups use a network of friends, many of whom act like persuasive salesmen, to help recruit.
One man who filled that role in Minneapolis, by one account, was Zakaria Maruf.
Stephen Smith, an attorney who represents several young Somalis questioned by authorities, said his clients describe Maruf as someone with a bravado that appealed to younger men he met on the basketball court or at mosques.
Smith said one of his 18-year-old clients got a phone call from Maruf, in Somalia, asking him to join the fight. Maruf and the teenager also exchanged e-mails and had a brief conversation in a chat room, Smith said.
Smith said the teen didn't go but felt uncomfortable turning down someone he looked up to.
Maruf's whereabouts aren't known. Some family members say they believe he was killed in Somalia last month, but federal officials could not confirm that.
Many young Somalis in Minneapolis say friends who left have stayed in touch through Facebook or phone calls. In those conversations, friends said, the men talked about life in Somalia being harder than expected, and of missing American food and Starbucks.
The Facebook accounts are private. While the FBI said it can't comment on specific communications, spokesman E.K. Wilson said the agency continues to investigate "who or what motivated" the young men to go to Somalia.
In Minnesota, imams are trying to counter al-Shabab's message by speaking out against violence and radicalism, reminding the faithful that Islam is peaceful.
Farhan Hurre, the executive director of Minneapolis' Abubakar As-Saddique Islamic Center, which has rejected suspicions it played a part in recruiting, said mosque leaders also are advising parents to keep their eyes open.
"If you have computers, if you have Internet, you have to know the sites that your boys are visiting and what they are listening to," Hurre said.