A former Army soldier from Phoenix who joined rebels fighting the Syrian government and boasted to FoxNews.com of his exploits as a Muslim soldier of fortune earlier this month was arrested Wednesday in Virginia and could face life in prison.

Eric Harroun, 30, who left the Army in 2003 on full disability pay after a truck accident, was charged with conspiring to use a rocket-propelled grenade while fighting with the al-Nusrah Front, an organization also known as Al Qaeda in Iraq. Harroun, who was in Syria or Turkey when he spoke to FoxNews.com by Skype, was nabbed shortly after flying in to Dulles International Airport after a voluntary interview with FBI agents, according to a criminal complaint filed Thursday.

Harroun could not be reached for comment, and the U.S. Attorney’s Office for the Eastern District of Virginia could not say if an attorney had been assigned to him. His father told FoxNews.com he was unaware his son was even back in the U.S.

“I was worried that he was dead,” Darryl Harroun said. “I don’t know anything about this.”

Harroun told FoxNews.com in an exclusive report March 11 that he considers himself a Muslim freedom fighter fighting the regime of Bashar Assad, which the U.S. also opposes. But breaking the law cited by prosecutors who charged him carries a possible life sentence.

“Any national of the United States who, without lawful authority, uses, or threatens, attempts, or conspires to use, a weapon of mass destruction outside of the United States shall be imprisoned for any term of years or for life, and if death results, shall be punished by death, or by imprisonment for any term of years or for life,” reads the law.

According to court documents, FBI agents conducted three interviews with Harroun this month after he voluntarily came to the U.S. Consulate in Istanbul. Harroun allegedly told the FBI that he wound up with the Al Qaeda affiliate after his rebel group was attacked, and was treated like a prisoner before being accepted. He told agents he shot at least 10 people in Syria, but said he didn’t know how many, if any, were killed, according to prosecutors.

Harroun was last interviewed in Istanbul on March 25, and two days later flew back to the U.S. where he was arrested at Dulles International Airport after telling the FBI he had used an RPG to take down a tower on “at least one occasion.”

Harroun appeared in federal court Thursday in Alexandria, Va., before U.S. Magistrate Judge Theresa Buchanan.

In the March 11, report, FoxNews.com chronicled Harroun’s transition from U.S. soldier to jihadist.

“I was separated in a battle and most of my group was KIA and Al-Nusra picked me up,” Harroun told FoxNews.com during one of several brief interviews conducted via Skype.

Harroun at the time shrugged off a question about fighting alongside Al Qaeda terrorists who have joined the Syrian rebellion, saying, "the U.S. plays both sides, too." He said the offshoot of the terror group behind the 9/11 attacks welcomed him.

“Getting into Al-Nusra is not rocket science," he said. "It just takes balls and brains.”

Harroun, known among Syrian rebels and loyalists alike as “The American,” has moved from one country to another, joining protesters in the takedown of Egyptian President Hosni Mubarak before fighting alongside rebels attempting to depose Syria’s Bashar al-Assad. A prolific poster of online diatribes against the infidel, he's joined the threads of those calling for the deaths of Zionists.

Darryl Harroun told FoxNews.com that his son was discharged from the Army after he was seriously injured while riding in a pickup truck that hit a tree. He was left with full disability pay and a steel plate in his head, according to his father.

"Now he has mood swings and what-not," said Darryl Harroun. "He was already suffering from depression before that, and the accident just kind of multiplied it."

Darryl Harroun said his son is seen as an adventurer by friends and relatives, who call him "Arizona Jones."

"He just loves that part of the world," said Darryl Harroun, who said his family has been in the U.S. for several generations and is not Muslim. "We scratch our heads and wonder what the hell he's doing. I told him, 'You're never going to change those people's minds over there.' But he says they treat him like a hero.

In the months before his arrest, Harroun appeared in several online videos alongside Syrian rebels fighting in Damascus and claimed to have personally killed several Shabiha (supporters of the Assad regime), Syrian soldiers and an Iranian.

“I hate bad guys like Bashar [Assad]," Harroun told FoxNews.com. "I hate Iran, too. I am a freedom fighter."

In one video posted online, Harroun is seen on the Syrian battlefield, speeding toward a downed helicopter in a Jeep detailed with a Free Syrian Army emblem on its windshield.

The FSA is a conglomerate of militia-style groups and former Syrian military personnel, according to Rafael Green, a research fellow at the Middle East Media Research Institute. Green said the FSA cooperates with groups such as Jabhat al-Nusra, and is not particular about who takes up its cause

Greg Tepper (@GregTepper1), a freelance journalist based in Israel, and Ilan Ben Zion (@ilanbenzion), a reporter for the Times of Israel, contributed to this report.