An Army psychiatrist suspected of opening fire on fellow soldiers at Fort Hood cleaned out his apartment in the days before the rampage that left 13 people dead, a neighbor said Friday.

The neighbor, Patricia Villa, said Maj. Nidal Malik Hasan came over to her apartment Wednesday and Thursday and offered her some items, including a new Koran, saying he was going to be deployed on Friday.

Authorities said the 39-year-old Hasan went on a shooting spree later Thursday at the sprawling Texas post.

He was among 30 people wounded in the rampage and remained hospitalized Friday in a coma, attached to a ventilator. All but two of the injured were still hospitalized, and all were listed in stable condition.

SLIDESHOW: Deadly Fort Hood Rampage

Investigators were trying to piece together how and why Hasan allegedly gunned down his comrades in one of the worst mass shootings ever on an American military base.

His motive wasn't known, but some who knew Hasan said he may have been struggling with a pending deployment and faced pressure in his work with distressed soldiers.

Hasan's family said in a statement Friday that his alleged actions were "despicable and deplorable" and don't reflect how the family was raised. Hasan and his family are of Palestinian descent.

President Barack Obama ordered the flags at the White House and other federal buildings be at half-staff and urged people not drawn conclusions while authorities investigate.

"We don't know all the answers yet. And I would caution against jumping to conclusions until we have all the facts," Obama said in a statement.

The shooting spree began as some 300 soldiers had been lined up to get vaccinations and have their eyes tested at a Soldier Readiness Center, where soldiers who are about to be deployed or who are returning undergo medical screening.

Nearby, others were lining up in commencement robes for a ceremony to celebrate troops and families who had recently earned degrees.

Soldiers reported that the gunman shouted "Allahu Akbar!" — an Arabic phrase for "God is great!" — before opening fire, said Lt. Gen. Robert Cone, the base commander. He said officials had not yet confirmed that Hasan made the comment.

The gunman was struck four times by a civilian police officer who also was wounded herself. Authorities said Kimberly Munley fired on the suspect just three minutes after the gunfire began, and base officials said her efforts ended the crisis. Munley was recovering Friday at a hospital and was in stable condition.

"It was an amazing and aggressive performance by this police officer," Cone said.

Hagerman said he saw Hasan laying on the ground receiving medical assistance for a gunshot wound as responders tried to get his handcuffs off to better treat him.

Hasan reported for duty at Fort Hood in July, after working at Walter Reed Army Medical Center in Washington for six years. Though Hasan apparently had problems at Walter Reed, officials at the Fort Hood hospital said they weren't aware of any issues with his job performance.

One of Hasan's bosses praised his work ethic and said he provided excellent care for his patients.

"Up to this point I would consider him an asset," said Col. Kimberly Kesling, deputy commander of clinical services at Darnall Army Medical Center.

An imam from a mosque Hasan regularly attended said Hasan, a lifelong Muslim, was a committed soldier, gave no sign of extremist beliefs and regularly wore his uniform at prayers.

Villa, who recently moved next door to Hasan, said she had never spoken to him before he came over to her apartment.

She said Hasan gave her frozen broccoli, spinach, T-shirts and shelves on Wednesday, then returned Thursday morning and gave her his air mattress, several briefcases and a desk lamp. He then offered her $60 to clean his apartment Friday morning, after he was supposed to leave.

Someone who used to work with Hasan said he had expressed some anger about the wars in Iraq and Afghanistan.

Retired Col. Terry Lee told Fox News said Hasan had hoped President Barack Obama would pull troops out of Afghanistan and Iraq and got into frequent arguments with others in the military who supported the wars.

Col. Steve Braverman, the Fort Hood hospital commander, said early Friday that Hasan was on deployment orders to Afghanistan. A military official later told The Associated Press that Hasan was to be deployed to Iraq. It was not immediately possible to verify the discrepancy.

The military official, who did not have authorization to discuss the matter publicly and spoke to the AP on condition of anonymity, said Hasan had indicated he didn't want to go to Iraq but was willing to serve in Afghanistan.

Cone said authorities have not yet been able to talk to Hasan, but interviews with witnesses went through the night.

Officials are not ruling out the possibility that some of the casualties may have been victims of "friendly fire," that in the confusion at the shooting scene some of the responding military officials may have shot some of the victims.

Cone acknowledged that it was "counterintuitive" that a single shooter could hit so many people, but he said the massacre occurred in "close quarters.

"With ricochet fire, he was able to injure that number of people," Cone said. He said authorities were investigating whether Hasan's weapons were properly registered with the military.

The wounded were dispersed among hospitals in central Texas, Cone said. Their identities and the identities of the dead were not immediately released.

Friday was designated a day of mourning at Fort Hood. There also will be a ceremony at the air base to honor the dead.

Hasan, who was born in Northern Virginia, pursued a career in psychiatry at Walter Reed, working as an intern, a resident and, last year, a fellow in disaster and preventive psychiatry. The Army major received his medical degree from the military's Uniformed Services University of the Health Sciences in Bethesda, Md., in 2001.

But his record at Walter Reed wasn't sterling. He received a poor performance evaluation, according to an official who spoke on condition of anonymity because he was not authorized to discuss the case publicly. And while he was an intern, Hasan had some "difficulties" that required counseling and extra supervision, said Dr. Thomas Grieger, who was the training director at the time.

Faizul Khan, a former imam at a mosque Hasan attended in Silver Spring, Maryland, said "I got the impression that he was a committed soldier." He said Hasan attended prayers regularly at the mosque and was a lifelong Muslim. He spoke often with Hasan about Hasan's desire for a wife.

In an interview with The Washington Post, Hasan's aunt, Noel Hasan of Falls Church, Va., said he had been harassed about being a Muslim in the years after the Sept. 11, 2001, terror attacks, and he wanted out of the Army.

"Some people can take it and some people cannot," she said. "He had listened to all of that and he wanted out of the military."