(RNS) Muslim groups quickly condemned the shootings by a Muslim suspect that killed 13 people Thursday (Nov. 5) at an Army base in Texas.

Maj. Nidal Malik Hasan, 39, a psychiatrist who treated soldiers at the Fort Hood base, is accused in the attack that also wounded 30 people. He survived and is hospitalized.

“No political or religious ideology could ever justify or excuse such wanton and indiscriminate violence,” said Nihad Awad, national executive director of the Council for American-Islamic Affairs. “The attack was particularly heinous in that it targeted our nation’s all-volunteer army that includes thousands of Muslims in all services.”

Awad cautioned against backlash towards Muslims, noting that the suspect’s motives are not yet known.

“We urge all Americans to remain calm in reaction to this tragic event and to demonstrate once again what is best about America — our nation’s ability to remain unified even in times of crisis,” he said.

Mahdi Bray, executive director of Muslim American Society Freedom, expressed his organization’s “shock” and “deep sadness” about the attack in a letter of condolence to the base commander.

“This unprovoked and unconscionable act of violence against American military personnel and civilians alike is utterly reprehensible, and against every tenet of faith and morality,” he wrote.

Hasan frequently attended prayer services at the Muslim Community Center in Silver Spring, Md., when he worked at Walter Reed Army Medical Center in Washington before moving out of the area.

“He was a very quiet and private person. I can’t say that people knew him very well other than attending prayers,” Arshad Qureshi, chairman of the mosque’s board of trustees, told The Washington Post. “He did not go out of the way to engage people. We have thousands of people who come through to pray; he was just one of them.”

The mosque was established in 1976 and offers a variety of community services, including a medical clinic.