Law enforcement officials have identified the young man arrested in connection with the terror scare at the Pentagon as 22-year-old Marine reservist Yonathan Melaku.
Melaku, of Alexandria, Virginia, was taken into custody overnight in Arlington National Cemetery -- less than a mile from the Pentagon -- while in the possession of suspicious materials and notes making reference to al Qaeda, law enforcement sources said, sparking a bomb scare near the heart of the American military.
Sources told ABC News a backpack in Melaku's possession contained a package labeled ammonium nitrate as well as spent firearm ammunition. Ammonium nitrate, a common fertilizer, can be used in explosives. The FBI later said despite the label, the backpack presented no immediate threat. A search of Melaku's nearby car also found no potential devices. Law enforcement sources said Melaku does not appear to have known ties to any terror organization.
In addition to his arrest today, Melaku already faces pending charges in Loudoun County, Virginia, for a rash of vehicle break-ins, police said.
Melaku is a naturalized U.S. citizen and joined the U.S. Marine Reserves in 2007 where he has risen to the rank of Lance Corporal in the Combat Engineer Support Company, according to the FBI. He has never been deployed abroad, but was awared the National Defense Service Medal and the Selected Marine Corps Reserve Medal.
The FBI said he is being held by the United States Park Police for trespassing.
Melaku is listed in public records as living with relatives in a nearly half-million dollar home in a small private community in Alexandria. There, federal authorities were spotted interviewing several people including two adults near the home for more than an hour. The pair was later put in the backseat of an unmarked car and driven away. The FBI later said a residence connected to Melaku had been searched.
An attorney for Melaku in his previous run-in with the law was not available for comment on this report.
ABC News' Sunlen Miller contributed to this report.