ISTANBUL

The family of the suspect in Sunday’s Michigan church attack is cooperating with the FBI as investigators search for the motive behind the assault, which killed at least four people, White House Spokesperson Karoline Leavitt said.

"His family is cooperating with the FBI, and so they are currently trying to dig in and get to the bottom of why he committed this heinous act of violence," Leavitt told Fox News Monday, speaking of Thomas Jacob Sanford, 40, who was killed by law enforcement officers at the scene.

Sanford was a US Marine Corps veteran who served in Iraq from 2004 to 2008 as a mechanic and vehicle recovery operator, according to military records.

"What we know at this point in time is that he was a member of this Michigan community, that he is a veteran of our United States Armed Forces. He served in the United States Marine Corps in Iraq," Leavitt confirmed.

FBI Director Kash Patel said investigators are executing multiple search warrants at the suspect's residences and family homes to determine his motive, according to Leavitt.

During Sunday morning worship services, Sanford drove his vehicle through the front doors of The Church of Jesus Christ of Latter-day Saints – also known as Mormons – in the Grand Blanc Township before opening fire, killing four and injuring at least eight others.