"It is a crime that would have horrified us had its victims been Americans of any background," Obama said. "But it's all the more heartbreaking and all the more despicable because of the place where it occurred and the patriots who were its victims."
The president was a baffled as the rest of the country by the bloody burst of violence.
"We cannot fully know what leads a man to do such a thing," Obama said.
Obama is planning to attend the memorial service on Tuesday at Fort Hood. He has also ordered flags to be flown at half staff in Washington and at military bases around the world through Veterans' Day in honor of the fallen.
The Pentagon official said investigators are not seeing one single motive for Hasan's bloody outburst.
"I think it will be a mixed picture," the official said. He cited Hasan's possible stress as a psychiatrist wroking with war victims at Walter Reed Hospital, and the increasing conflict between his devout religious beliefs and being a soldier. Hasan is a Muslim.
Bono, who was released from the hospital Friday, said she is still planning on her deployment.
"I still have a duty to perform and if my commander is still willing to let us go, then yes I'm going to go," she said.
As for Hasan, Bono said she really hadn't stopped yet to be angry.
"I think he's very selfish, what he did," she said.
American Muslims were braced for a backlash after Hasan's deadly shooting spree.
Army veteran Osman Danquah, a Muslim, said Hasan was soft spoken, but was obviously conflicted about the Army's participation in the war on terror.
"I wasn't much impressed with him when we had a couple of conversations," Danquah told "GMA."
Danquah said Hasan wanted to know, as a psychiatrist, what he was supposed to tell soldiers who had resentment about going to war.
"My response was that it's volunteers," Danquah said. "It's an all volunteer Army. No one is drafted into the Army."
Hasan's cousin, Nader Hasan, issued a statement late Thursday.
"We are shocked and saddened by the terrible events at Fort Hood today. We send the families of the victims our most heartfelt sympathies," the statement read. "Nidal was an American citizen. He was born in Arlington, Va., and raised here in America. ... Our family loves America. We are proud of our country, and saddened by today's tragedy."
Nader Hasan said that she believed it was his upcoming deployment combined with the wartime horror stories he heard from his patients that set him off.
Hasan had reportedly recently hired an attorney to help him get out of the military.
According to the suspect's cousin, Hasan was also harassed after 9/11 because of his ethnicity, and was called a "camel jockey."
An Army official confirmed that Hasan would have been deployed to Afghanistan later this month. Sources told ABC News that this would have been his first deployment.
ABC News' Martha Raddatz contributed to this report