WASHINGTON — Investigative officials said the Army psychiatrist accused of the Fort Hood massacre apparently was a lone wolf, acting alone and without outside direction in the attack.

Officials also said Maj. Nidal Malik Hasan will be charged by the U.S. military rather than in a civilian court.

Investigators said Hasan communicated 10 to 20 times with a radical cleric overseas who in the past came under scrutiny for possible links to terror groups. But the investigative officials said the communications "were consistent with the subject matter of his research" on the effects of U.S. combat operations in Iraq and Afghanistan.

A U.S. official told The Associated Press the Fort Hood shooting suspect reached out to communicate with a radical imam overseas who came under scrutiny in the past for possible links to terror groups.

The official, who spoke on condition of anonymity because the person was not authorized to discuss the investigation, said Hasan sent electronic communications to Anwar al Awlaki. Awlaki writes a blog which, among other things, denounces U.S. policies as anti-Muslim.

The official said the messages were picked up by U.S. counterterrorism officials, but that an inquiry into the matter was shelved because the contacts were not deemed to suggest a threat. Investigators are trying to determine whether Nidal has any links to terror groups.

Investigators said U.S. officials were aware of the communications since last year, but no formal investigation was ever opened based on them. The officials said that FBI Director Robert Mueller has ordered an internal review of the bureau's handling of the Hasan information.