Some of the people who knew Maj. Nidal Malik Hasan, the Army psychiatrist accused of killing 13 people and wounding 29 others in a shooting spree at Fort Hood military base in Texas, say they were concerned he did not belong in the military.

While he was a student in a military medical program, classmates complained to their instructors after Hasan expressed anti-American views. But they stopped short of filing a formal complaint in order to avoid the appearance that they were discriminating against a Muslim colleague.

When Hasan spoke with Osman Danquah, a community leader in nearby Greater Killeen, Texas, he was given blunt advice.

"I told him, 'There's something wrong with you,"' Danquah said in an interview with The Assocaited Press. "I didn't get the feeling he was talking for himself, but something just didn't seem right."

In one classroom presentation, Hasan reportedly argued that suicide bombings were justified. He also complained of being persecuted by the military because of his Muslim beliefs.

No charges have been laid against Hasan, and military officials continued to refer to him as a suspect in the shooting spree late on Saturday.

Meanwhile, Hasan's family defended his character.

"I've known my brother Nidal to be a peaceful, loving and compassionate person who has shown great interest in the medical field and in helping others," his brother, Eyad Hasan, wrote, in a statement. "He has never committed an act of violence and was always known to be a good, law-abiding citizen."

Presidential response

In his Saturday address, U.S. President Barack Obama called for patience as investigators search for a motive in the shootings.

"We cannot fully know what leads a man to do such a thing," Obama said. "But what we do know is that our thoughts are with every one of the men and women who were injured at Fort Hood. Our thoughts are with all the families who've lost a loved one in this national tragedy."

Obama hailed the diversity of his country's military, and praised the heroism of those who rushed to the aid of soldiers who were gunned down at the military base on Thursday.

"They are Americans of every race, faith and station. They are Christians and Muslims, Jews and Hindus and nonbelievers," Obama said. "They reflect the diversity that makes this America. But what they share is a patriotism like no other."

Obama said he plans to attend a memorial service for the victims, likely on Tuesday. However, the White House said the exact time will be decided by the victims' families.

Military officials allege Hasan opened fire at the base with a semi-automatic pistol. About 100 rounds were unleashed on unsuspecting soldiers before a policewoman fired at Hasan, hitting him at least four times.

It is the worst mass shooting ever on a U.S. military base.

Hasan has been transferred to Brooke Army Medical Center in San Antonio, CNN reporter Sean Callebs told CTV News Channel via telephone on Saturday morning.

Later in the day, an Army spokesperson said Hasan had been taken off a ventilator but remained in intensive care.

Soldiers recovering

As of Saturday afternoon, most of those wounded in the attack remained in hospital. Many were still in intensive care.

Former president George W. Bush and his wife, Laura, visited the wounded at the post hospital on Friday night.

On Saturday morning, Texas Governor Rick Perry visited the soldiers and their families, an experience he described to reporters afterward as "humbling."

According to Perry, local residents stood in line for hours to donate blood to assist the wounded, just one sign that "there's 24 million Texans praying for them and wishing them well."

Officials set up a grief counselling centre at the nearby Killeen Community Center to help residents cope in the aftermath of the shooting.

At a candlelight vigil Friday evening, a U.S. Army chaplain urged soldiers to "keep going" in the wake of the deadly shooting spree.

Several hundred soldiers, many dressed in fatigues and black berets, and civilians gathered at the base's sports stadium to honour the dead and injured.

Investigators must now determine what motivated the shooting. They spent Friday searching Hasan's apartment, his computer and his garbage.

A neighbour told the media that Hasan had cleared out his apartment and had offered her some of his possessions.

Witnesses have said Hasan stood on a desk at the Soldier Readiness Processing Center, where troops being deployed to Iraq or Afghanistan, or are returning home, undergo medical testing, and opened fire around 1:30 p.m. local time.

According to some witnesses the gunman shouted "Allahu Akbar!" -- an Arabic phrase for "God is great!" -- before opening fire. However, officials had not yet confirmed the reports.

There are also reports that Hasan was unhappy about a pending deployment to Afghanistan. However, an uncle living in the West Bank, Rafik Hamad, told the Associated Press that Hasan was happy to serve his country.

With files from The Associated Press