WASHINGTON — on Thursday, June 12,  a 17-year-old from Virginia pleaded guilty in court to charges of conspiring to help Islamic State militants, the first time the United States has prosecuted a minor as an adult in such a case.

Ali Amin, of Manassas, Virginia, used Twitter and his blog to provide instructions on how to use the virtual currency Bitcoin to send funds to the militants, according to court documents. His Twitter account had more than 4,000 followers.

Prosecutors said Amin also helped another Virginia resident, Reza Niknejad, to travel to Syria to join the group that has taken control of areas of Iraq and Syria over the past year in a campaign marked by mass killings and beheadings.

Dana Boente  U.S. Attorney for the Eastern District of Virginia told a press conference that the magnitude of the charges led to prosecution of Amin as an adult.

“It’s something we take very very seriously, the age of someone…but at the end of the day, it’s a matter of public safety,” Boente said.

Amin’s lawyer, Joseph Flood, described Amin as a “good guy” who was sympathetic to the opposition against Syrian President Bashar al-Assad in Syria’s civil war and got wrapped up in the wrong thing online.

Wearing a prison uniform on his thin frame, Amin appeared calm and polite as he pleaded guilty to the charges. His mother, also in the courtroom, stayed silent and showed little emotion.

Amin faces up to 15 years in prison when he is sentenced on Aug. 28.

“This case serves as a wake-up call that ISIL’s propaganda and recruitment materials are in your communities and being viewed by your youth,” Assistant Attorney General John Carlin said in a statement, using an acronym for “Islamic State.”

Northern Virginia has a large Muslim community. Anwar al Awlaki, an American linked to Yemen’s al Qaeda branch, preached at a mosque there before leaving the United States shortly after the Sept. 11, 2001 attacks. He was the first U.S. citizen the White House authorized U.S. agencies to kill overseas.

Andrew McCabe, assistant director of the FBI’s Washington field office, said Amin was a “promising young man” who was active in his local mosque and helpful to his family. He said the FBI became aware of Amin in November.

Amin made travel arrangements for Niknejad and drove him to Dulles International Airport in January, prosecutors said. Niknejad is still at large and prosecutors filed terrorism-related charges against him on Wednesday.