FORT HOOD, Texas (AP) — An Army psychiatrist suspected of opening fire on fellow soldiers at Fort Hood cleaned out his apartment and left a phone message saying goodbye to a friend in the days before the rampage that left 13 people dead, neighbors said Friday.

One neighbor, Patricia Villa, said Maj. Nidal Malik Hasan came over to her apartment Wednesday and Thursday and offered her some items, including a new Quran, 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; all were in stable condition.

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. Though his motive wasn't known, some who knew Hasan said he may have been struggling with a pending deployment to Afghanistan 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.

President Barack Obama ordered the flags at the White House and other federal buildings be at half-staff and urged people not to draw 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 troops 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 soldiers 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 confirmed that Hasan made the comment.

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

When the gunfire subsided, soldiers described a scene that looked like a war zone: too many wounded to count, shells and blood on the floor, and comrades ripping off their clothes to make tourniquets to keep the injured alive. One woman, suffering from a wound to the hip, carried another victim to get help.

"You had people without tops on. You had people ripping their pant legs off," said Sgt. Andrew Hagerman, a military police officer from Lewisville, Texas.

Hagerman arrived at the scene minutes after the shooting stopped. When he entered the building, he kept his head down to avoid stepping in the pools of blood or kicking any spent shell casings.

"You could go around it," he said. "There was definitely a path."

The gunman was struck four times by a civilian police officer who was wounded herself. Base officials said Kimberly Munley fired on the suspect just three minutes after the gunfire erupted and that her efforts ended the crisis. Munley was recovering Friday at a hospital.

"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 he apparently had problems at Walter Reed, Fort Hood officials 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.

Neighbors described a man who appeared to be getting his affairs in order just hours before the shooting. Hasan was set to deploy to Afghanistan with an Army Reserve unit that provides what the military calls "behavioral health" counseling, Army spokeswoman Col. Cathy Abbott said.

Villa, who moved next door to Hasan about a month ago, 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.

Another neighbor received a phone message from Hasan at 5 a.m. Thursday.

Jacqueline Harris, 44, said Hasan called her boyfriend, Willie Bell. "He just wanted to thank Willie for being a good friend and thank him for being there for him," Harris said. "That was it. We thought it was just a nice message to leave."

The manager of the apartment complex said Hasan recently was involved in a spat with another soldier living there over Hasan's religious beliefs. A bumper sticker that read "Allah is Love" was ripped off Hasan's car, which was keyed, said the manager, John Thompson.

Thompson said the neighbor had been in Iraq and was upset to learn that Hasan was Muslim.

Hasan's mindset about his mission overseas wasn't clear. Someone who used to work with Hasan said he had expressed some anger about the wars in Iraq and Afghanistan, but neighbors said he appeared fine with his pending deployment.

"I asked him how he felt about going over there, with their religion and everything, and he said, 'It's going to be interesting,'" said Edgar Booker, a retired soldier who now works in a cafeteria on the post.

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

The wounded were dispersed among hospitals in central Texas. The dead included a man who quit a furniture company job to join the military about a year ago, a newlywed who had served in Iraq and a woman who had vowed to take on Osama bin Laden after the Sept. 11 terrorist attacks.

U.S. Muslims reacted with both anger and fear of backlash after revelations that Hasan is a practicing Muslim. The nation's major Muslim organizations and several mosques quickly condemned the attacks as contrary to Islam and highlighted the military service of U.S. Muslims, including those who have been killed in Iraq and Afghanistan.

"The community is in a state of agony," said Muqtedar Khan, director of the Islamic studies program at the University of Delaware and a well-known progressive Muslim intellectual.

Some U.S. mosques stepped up security on Friday, the main prayer day for Muslims.

Hasan, who was born in Northern Virginia, pursued a career in psychiatry at Walter Reed, working as an intern, a resident and 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.

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."

At least six months ago, Hasan came to the attention of law enforcement officials because of Internet postings about suicide bombings and other threats, including posts that equated suicide bombers to soldiers who throw themselves on a grenade to save the lives of their comrades.

Investigators had not determined for certain whether Hasan was the author of the posting, and a formal investigation had not been opened before the shooting, said law enforcement officials who spoke on condition of anonymity because they are not authorized to discuss the case.

Federal authorities seized Hasan's computer Friday during a search of his apartment, said a military official who spoke on condition of anonymity because of the ongoing investigation.

Baker reported from Killeen, Texas. Associated Press Writers Lara Jakes, Devlin Barrett, Brett J. Blackledge, Eileen Sullivan and Ben Feller in Washington, Allen Breed and April Castro in Killeen, Matt Curry in Dallas and Eric Gorski in Denver contributed to this report.