Imam Faizul Khan said he knew Maj. Nidal Malik Hasan for more than 10 years. They met at the Muslim Community Center in Silver Spring.

Mr Khan said he was shocked and dismayed to find the person suspected in the incident was his old friend.

"I keep asking what could have made him do something like that? I was stunned and very surprised," he said.

"These are not the actions of a good Muslim at all."

Mr Kahn said Maj Hasan was quiet and reserved. The pair mostly discussed religious matters and rarely talked about politics, but Hasan never seemed controversial, he said.

He said Maj Hasan often talked about wanting a wife.

On a form filled out by those seeking spouses through a program at the mosque, Mr Kahn said Maj Hasan listed his birthplace as Arlington, Va., but his nationality as Palestinian.

Mr Khan also said the psychiatrist applied to an annual matrimonial seminar that matches Muslims looking for spouses. "I don't think he ever had a match, because he had too many conditions," Mr Khan said.

Maj Hasan was a lifelong Muslim and attended prayers regularly, often in his Army uniform, he said.

On its website, the Muslim Community Center advertises Hajj workshops, Arabic language classes and lectures.