The Justice Department has filed charges against Ahmed Kattalah, a Libyan militia leader long thought to be a key player in orchestrating the attack on the U.S. diplomatic compound in Benghazi, Libya, according to a news report on CNN.

Kattalah is the founder of the Islamist militia Ansar al-Sharia, an al Qaeda-affiliated terrorist group that absconded with Ambassador Chris Stevens the night of the attack. It is not known if Stevens had already died before the militia group took him to a hospital it runs after setting fire to the compound and killing three other U.S. citizens that night.

The order detailing the charges is under seal, CNN reports, so it's not clear whether he is the only suspect to be charged, what specific charges he'll face or whether the U.S. plans to detain him.

Ansar al-Sharia has denied it orchestrated or participated in the violence, but Gregory Hicks, the deputy chief of mission at the U.S. Embassy in Libya, testified before Congress in early May that a Libyan official told him the night of the attack that Stevens had been taken to the hospital run by Ansar al-Sharia.

Even though U.S. officials have known for months that Kattalah was at the U.S. consulate compound the night of the deadly attack, he has remained free as U.S. authorities struggled to investigate the killings and bring the perpetrators to justice, as President Obama vowed to do the day after the Sept. 11 attack.

The Justice Department refused to confirm that charges have been filed in the Benghazi case.

“The department’s investigation is ongoing. It has been, and remains, a top priority. We have no further comment at this time,” said DOJ spokesman Andrew Ames.

Ansar al-Sharia became the focus of the FBI investigation after intelligence officials disclosed they overheard members of the group bragging about the incident on phone calls with al Qaeda leaders in Northern Africa just after the Sept. 11 attack on the diplomatic post.

CNN recently interviewed Khattala, prompting Republicans to demand to know why U.S. investigators have not captured or killed any of the suspects in the Benghazi attack.

Before news broke of the charges, the FBI had only identified Khattalah as a “person of interest.”

During his interview with CNN, Khattala said he had not been contacted by any Libyan or American officials.

“Even the investigative team did not try to contact me,” he said, referring to the FBI.

Khattalah also said he would have agreed to meet with U.S. officials if they had asked and if he were not being interrogated.

“Yes, no problem,” he said. “...But not as an interrogation, as a conversation like the one we are having right now.”

Khattala reportedly talked to CNN for two hours at a coffee shop at a hotel in Benghazi. He allowed the reporter to use an audio recorder but refused to appear on camera, even though his mood was fairly relaxed.

During the interview, he admitted to being at the compound the night of the attack, but denied any involvement in the violence.

When asked whether he had masterminded the attack, Khattala and two of the men accompanying him for the interview “burst out laughing,” CNN reported.

He also has granted interviews with the New York Times, Reuters and other news agencies in the weeks following the Benghazi attack.

About a month after the attack and just days after Obama reiterated his pledge to bring those responsible to justice, Khattala talked to the New York Times for two hours at a crowded hotel, sipping a strawberry frappe on a patio and scoffing at the threats coming from the U.S. and Libyan governments.