When he allegedly exchanged emails with Colleen LaRose, the woman known as Jihad Jane, the young man was 15 and a good student who spent a lot of time at his computer in a quaint bedroom community outside Baltimore.
Now 17, the teenager from Ellicott City, Md., was arrested last month and charged with helping LaRose plot to kill a Swedish cartoonist who offended Muslims, said two sources who spoke on the condition of anonymity because they were not authorized to speak publicly about the case.
LaRose pleaded guilty in February to conspiring to provide material support to terrorists.
The sources identified the suspect, whose name is not being published because he is a juvenile, as co-conspirator No. 4 in charging documents against LaRose. The charges against him are under seal, also because of his age.
In an online message posted July 8, 2009, the teen allegedly solicited money to help LaRose plot an attack.
"I write this message on behalf of a respected sister," he allegedly wrote in an appeal for "urgent funds," according to court documents.
The arrest was first reported Friday by the Philadelphia Inquirer.
The suspect's family told the Inquirer that they had made "a mistake" in allowing him be questioned at least eight times by the FBI without a lawyer or relative present.
The teen was born in Pakistan and came to the U.S. with his family four years ago. He was admitted to Johns Hopkins University in Baltimore, to begin in September.
Federal prosecutors are attempting to persuade the judge in the case to try the suspect as an adult, said a source familiar with the case.
He is being held in a juvenile detention center northwest of Philadelphia, where he is going through a standard mental health screening and evaluations.
"This is a juvenile case and the allegations are extremely serious, so it would be very inappropriate for me to comment on it," said Jeffrey M. Lindy, the suspect's court-appointed lawyer.
The Justice Department and the FBI had no comment.