A Minnesota man recruited to join an Al Qaeda-linked terrorist group overseas may have been assassinated in Somalia by the very terrorist group he went there to help.

The Federal Bureau of Investigation has been investigating for several months at least 20 Somali-American men from the Minneapolis area who recently traveled to Somalia to train with the terrorist group al-Shabaab.

One of those men — 17-year-old Burhan Hassan — was killed in Mogadishu on Friday, his uncle, Osman Ahmed, told FOX News.

"Someone who claimed (to be) a member of al-Shabaab called Burhan's mom Friday (afternoon) and said Burhan died Friday morning," Ahmed said. "Burhan's mom got shocked and (threw) the phone when she heard the story."

A spokesman from the FBI's Minneapolis field office declined to comment Monday.

"We are aware of the report to his family of this young man's death overseas, but cannot confirm it and cannot comment further due to our ongoing investigation," spokesman E.K. Wilson said.

A law enforcement official told FOX News on Sunday that one of the Somali-American men was recently killed in Somalia, but the official declined to release the man's name.

Ahmed said Hassan was killed by members of al-Shabaab. A leader in the Minneapolis Somali community said later that al-Shabaab members originally from the Minneapolis area were likely responsible for Hassan's death.

"Al-Shabaab assassinated Burhan and shot (him in) the head," Ahmed said. In fact, Hassan was shot "point blank," according to Omar Jamal, the executive director of the Somali Justice Advocacy Center in St. Paul, Minn.

Hassan's family last heard from him two weeks ago, according to Ahmed.

"That time he was sick, and he couldn't talk that much," Ahmed said. "He called his family and Burhan's voice was very weak, and then (a friend with him) ... told the family Burhan was sick a while and having malaria."

That sickness helped Hassan's family convince him to return to the United States, and he was set to fly to Nairobi, Kenya, later this week, according to Jamal.

"But the fact that he was about to leave made (al-Shabaab) feel threatened, and they took him out," said Jamal, who spoke with Hassan's family about the incident. "To others thinking about coming back it's a clear message: 'It's not going to be that easy.'"

Hassan's body was buried in Somalia over the weekend, but Jamal said he asked the FBI to help get the body returned to the United States. FBI officials told him they are "looking into it," he said.

Hassan was a senior at Roosevelt High School in Minneapolis when he left for Somalia late last year.

"(He) was a brilliant student with straight A's and on top of his class," Ahmed testified at a Senate hearing in March focusing on recruitment efforts by al-Shabaab. "He was an ambitious kid with the hope to go to Harvard University to study medicine or law and become a medical doctor or a lawyer."

Ahmed accuses a local mosque of helping al-Shabaab recruit his nephew and others in the Minneapolis area.

"Like his peers, Burhan Hassan was never interested in Somali politics, or understood Somali clan issues," Ahmed said during testimony. "These kids have no perception of Somalia except the one that was formed in their mind by their teachers at (a local mosque). We believe that these children did not travel to Somalia by themselves. There must be others who made them understand that going to Somalia and participating the fighting is the right thing to do."

Hassan is the second known American to die alongside al-Shabaab, which has been warring with the moderate Somali government since 2006.

In October 2008, 27-year-old college student Shirwa Ahmed of Minneapolis became "the first known American suicide bomber" when he blew himself up in Somalia, killing dozens, according to the FBI.

A source familiar with the FBI investigation told FOX News in March that "several" of the men who went to Somalia had returned to the United States, while others "are still there (in Somalia)."