AL-BIREH, West Bank (Reuters) - The grandfather of a U.S. Army psychiatrist accused of shooting dead 13 people and wounding 30 others at a base in Texas said on Saturday he found it impossible to believe his grandson had committed the act.

"He is a doctor and loves the U.S." Ismail Mustafa Hamad told Reuters in an interview at his home in the Palestinian town of al-Bireh. "America made him what he is."

U.S.-born Major Nidal Malik Hasan, 39, a Muslim and the son of immigrant parents, was shot during the attack and is being held at a hospital in San Antonio, Texas.

"Whether he became angry or something else, I don't know... What I do know is that it is impossible that he would do something like that," Hamad, 88, said.

Hasan, who had spent years counseling wounded soldiers, many of whom had lost limbs fighting in Iraq and Afghanistan, last visited him in the occupied West Bank some 10 years ago. Hamad said he had since visited his grandson in the United States.

Hamad appeared to rule out a political motive.

"He used to come to my house, to stay with me and entertain me. He never took an interest in politics and he didn't even like watching television," Hamad said.

WORST NIGHTMARE

Colonel John Rossi, a spokesman at the Fort Hood army base, the biggest military facility in the world, said Hasan was unconscious but in stable condition.

The gunman, with two guns including a semi-automatic weapon, opened fire apparently without warning at Fort Hood base, where troops were getting medical checkups before leaving for foreign deployments.

Hasan was transferred to Fort Hood in April and was to have been deployed to Afghanistan, where the U.S. military is fighting Taliban and al Qaeda.

Hasan's cousin, Nader Hasan, said in interviews that he had agitated not to be sent overseas. "We've known over the last five years that was probably his worst nightmare," he said.

Nader Hasan also said his cousin had complained, as a Muslim, of harassment by fellow soldiers.

Hasan yelled "Allahu Akbar" -- Arabic for "God is Greatest" -- just before the shooting, Chuck Medley, Fort Hood's director of Emergency Services, told Reuters.

Another cousin, Mohammed Hasan from al-Bireh, said the shooting may have been motivated by what he said was the U.S. Army's refusal to allow him to leave the armed forces.

"About a week before the incident, he hired a lawyer in order to leave the army, get married and live his life. But they rejected his request, and asked him to go to Afghanistan.

"This was the biggest shock for him. So there is another reason why he did what he did, not just because of the harassment of the soldiers, there is another reason," Mohammed Hasan said.

(Reporting by Ramallah bureau, Writing by Ori Lewis; Editing by Ralph Boulton)