Washington (CNN) -- Hakimullah Mehsud, a key leader of the Pakistani Taliban, has been charged for his alleged involvement in the killings of seven U.S. citizens at an American military base in Afghanistan in 2009, the U.S. Justice Department announced Wednesday.

A $5 million reward is being offered for information leading to the capture of Mehsud and another top Pakistani Taliban leader, Wali Ur Rehman, U.S. officials announced.

A complaint listed two criminal charges against Mehsud.

"We support any lawful means to hold this terrorist accountable for what he's done," CIA spokesman George Little said Wednesday. "The announcement today is part of that."

A U.S. official said the criminal charges are meant to deal with Hakimullah if he's captured, and added, "He can face justice in other ways, too. That hasn't changed." The "in other ways" comment was a backhanded reference to CIA Predator missile strikes in Pakistan, which have killed a number of suspected al Qaeda terrorists and other extremists.

The group -- which was declared a terrorist organization by the United States -- is believed to be responsible for terrorist acts, including the December 30, 2009, suicide attack on a CIA base in Afghanistan and the attempted Times Square bombing earlier this year.

A criminal complaint unsealed Wednesday details the U.S. government's case against Mehsud.

All the victims were killed by a suicide bomber, a Jordanian national named Humam Khalil Abu Mulal al-Balawi, at a U.S. base near Khost, Afghanistan.

The attack killed five CIA officers, two private military contractors working for the CIA, and a member of Jordanian intelligence. Also killed was the base chief, Jennifer Matthews, a 45-year-old mother of three.

U.S. officials believe Mehsud was working with al-Balawi in planning the attack as well as planning the failed bombing attack in Times Square in May.

The counts against Mehsud include conspiracy to murder a United States national while outside the United States and conspiracy to use a weapon of mass destruction against a national of the United States while outside the United States.

Mehsud is believed to be the commander of Tehrik-e-Taliban Pakistan, which a U.S. official described as a "Taliban-inspired alliance of Pakistan-based Sunni tribal militants." The group claimed responsibility for the suicide bombing as well as the failed attempt to bomb New York's Times Square.

FBI Investigators are piecing together their case based on interviews with survivors of the Afghan attack and details gleaned by combing through personal items left behind by the victims. It is believed that al-Balawi was working with Jordanian intelligence as a double agent, offering information to Jordanian and U.S. intelligence officials on the aftermath of drone attacks while garnering enough support and trust to carry out the suicide attack.

Witnesses told investigators that Al-Balawi was welcomed on the base in December before he exited the right side of the vehicle, reached under his clothing and detonated the device he had strapped to his body.

After the attack, a previously recorded video was released of Mehsud and al-Balawi together talking about the attack.

The U.S. government listed the Pakistani Taliban as a foreign terrorist organization, indicating its intent on going after terrorists one way or another.

"We have no higher priority than bringing to justice terrorists who kill Americans serving and working abroad," said U.S. Attorney Ronald C. Machen, Jr. in a news release. "We will continue to use every tool at our disposal to seek justice for the victims of this heinous arrack."

Complaints generally list the address of the accused. In this case, the accused's address reads "Federally Administered Tribal Area of Pakistan." And therein lies a problem.

Serving an arrest warrant against a suspected terrorist living in the tribal areas will be difficult. But the United States has added a financial incentive by offering the $5 million reward for information leading to the capture of Mehsud and Ur Rehman, another leader of the group.

CNN's Pam Benson contributed to this story.