Eric Harroun, a 30-year-old US Army veteran said to have been fighting alongside al-Nusra terrorists against the Assad regime in Syria, was charged Thursday in a Virginia court with conspiring to use a rocket-propelled grenade (RPG) while fighting with al-Nusra.

The US State Department considers al-Nusra an al-Qaeda alias.

According to Fox News Harroun was arrested after arriving at Dulles International Airport earlier this week. Harroun, the report said, was interviewed three times by the FBI in March at the US Consulate in Istanbul. He admitted to shooting at least 10 people in Syria, but didn’t know if any of them were killed.

Harroun was charged in federal court with conspiring to use a destructive device outside of the United States, which carries a maximum life sentence.

Harroun was allegedly trained to use an RPG by members of the terrorist organization and took part in attacks with members of al-Nusra.

Harroun had become known as “the American” and had featured in several videos fighting alongside anti-regime forces.

In a late-January clip, a man who was apparently Harroun threatened to kill Syrian President Bashar Assad whether or not he abdicates.

“Bashar Assad, your days are numbered,” he said. “You are going down in flames. You should just quit now, while you can, and leave. You are going to die, no matter what. Where you go we will find you and kill you. Do you understand?”

In a February clip, he and another fighter celebrate the apparent downing of a regime helicopter. “Yes, we smoked the motherfuckers, didn’t we?” the English-speaker says with a smile. “Hell, yeah. We smoked about — I don’t know — 10, 20.”

It is not clear how many Americans are fighting in the civil war against Assad, but the speaker in the video would not be the only one fighting alongside the Free Syrian Army. Matthew VanDyke, a self-proclaimed freedom fighter, participated in the uprising against Libyan dictator Muammar Gaddafi, and then fought in Syria, before returning to the United States.

The BBC also reported on two Syrian-American brothers who returned to Syria to fight against the Assad regime.