(FT HOOD) Military officials are starting to piece together what may have pushed an Army psychiatrist trained to help soldiers in distress to turn on his comrades in a shooting rampage that killed 13 people and wounded 30 at Fort Hood.

The suspected shooter, Maj. Nidal Malik Hasan, was on a ventilator and unconscious in a hospital after being shot four times during the shootings at the Army`s sprawling Fort Hood. In the early chaos after the shootings, authorities believed they had killed him, only to discover later that he had survived.

In Washington, a senior U.S. official said authorities at Fort Hood initially thought one of the victims who had been shot and killed was the shooter. The mistake resulted in a delay of several hours in identifying Hasan as the alleged assailant.

Authorities have not ruled out that Hasan was acting on behalf of some unidentified radical group, according to one official. He would not say whether any evidence had come to light to support that theory.

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

The gunfire broke out around 1:30 p.m. at the Soldier Readiness Center, where soldiers who are about to be deployed or who are returning undergo medical screening. Nearby, some soldiers were readying to head into a graduation ceremony for troops and families who had recently earned degrees.

The post went into lockdown while a search began for a suspect and emergency workers began trying to treat the wounded. Some soldiers rushed to treat their injured colleagues by ripping their uniforms into makeshift bandages to treat their wounds.

While the shootings were taking place, Killeen ISD put all Fort Hood schools on lockdown. Temple ISD was also placed on a "soft" lockdown.

Fort Hood Lt. Gen. Bob Cone says Fort Hood schools will be open on today, and Fort Hood is no longer on lockdown; people are allowed to come and go.

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

The Red Cross is urgently requesting blood donations.

The bodies of the victims would be taken to Dover Air Force Base in Delaware for autopsies and forensic tests.

There will also be a ceremony at the air base to honor the dead.

The motive for the shooting wasn`t clear, but Hasan was apparently set to deploy soon, and had expressed some anger about the wars in Iraq and Afghanistan.

The FBI, local police and other agencies searched Hasan`s apartment Thursday night after evacuating the complex in Killeen, and the case remains under investigation.

Texas Governon Rick Perry has ordered all flags to half staff until Sunday to honor the fallen.

The governor’s flag order applies to all U.S. and Texas flags under the control of the state. Flags will be lowered to half-staff on the State Capitol Building, flag displays in the Capitol Complex, and upon all public buildings, grounds and facilities beginning immediately until sunset on Sunday, November 8th.

Individuals, businesses, municipalities, counties and other political subdivisions are encouraged to fly the flag at half-staff for the same length of time as a sign of respect.