The Michigan State Police Bomb Squad prepare an armored vehicle near Thomas Sanford's house in Burton, Michigan.

Two days after worshippers at a church in Michigan were attacked in a hail of bullets and a wall of flames, authorities asked for patience as the search for a motive continued and a community reeled from the violence that claimed four lives.

The shooting unfolded the morning of Sept. 28 when police say gunman Thomas Jacob Sanford drove a truck bearing American flags through the front of The Church of Jesus Christ of Latter-day Saints chapel in Grand Blanc Township, Michigan, and opened fire on those inside. He is believed to have used gasoline to light a fire, which reduced much of the church to rubble.

Hundreds of people were inside the chapel at the time of the shooting, which is being investigated as an "act of targeted violence," according to the FBI. Four people were killed and eight others were injured, with one in critical condition. Sanford was killed in a gunfight with police.

Sanford, 40, was a military veteran who lived in nearby Burton, Michigan. White House Press Secretary Karoline Leavitt said in an appearance on "Fox and Friends" that Sanford "hated people of the Mormon faith" but did not elaborate. A local politician said a week before the attack Sanford went on a tirade against the church and referred to Mormons as "the Antichrist."

Michigan Gov. Gretchen Whitmer on Sept. 29 asked for patience as investigators continued to search for information about what may have motivated Sanford. "Speculation is unhelpful and it can be downright dangerous," Whitmer said.

'It's been a nightmare': Gunman's father apologizes after deadly attack

In an interview with the Detroit Free Press, part of the USA TODAY Network, Sanford's father, Thomas Sanford, apologized to the victims of the attack.

"I feel terrible about all the families that have been hurt and they're under the same crap that I'm going under, that my wife and I are going under," Sanford said, his voice breaking slightly. "I apologize for that."

Sanford said his son was devoted to his family and his country. He said he was glad his son "came back in one piece" after serving time in the Middle East, and wouldn't speculate on what may have driven him to attack the church.

"The only thing I can say is that it was my son that did it," Sanford said. "As far as why? Irrelevant. It happened. We're dealing with it. It's been a nightmare."

What happened in the Grand Blanc church shooting?

The shooting unfolded just before 10:30 a.m. on Sunday, Sept. 28, while hundreds of people were inside the chapel, authorities said.

Two law enforcement officers who responded to the scene within 30 seconds of the first 911 call shot and killed Sanford in the church parking lot within minutes of the shooting.

Two churchgoers died of gunshot wounds. The bodies of two other worshippers were discovered in the rubble of the chapel hours later.

Who are the victims?

Authorities have not publicly released the names of the victims killed in the attack, but families and friends have begun to identify their loved ones.

John Bond, 77, was one of four congregants killed in the attack, according to a GoFundMe created by his family. Bond, a Navy veteran, was remembered as a devoted husband, father and grandfather. "He was a well-known and loved member of his family and active in his community," the family wrote. “(He) always loved spending time with his family and grandkids."

At a news conference, Dr. Michael Danic, medical chief of staff at Henry Ford Genesys Hospital, told reporters that eight patients ranging in age from 6 to 78 were treated for gunshot wounds and smoke inhalation following the attack.

Who was Thomas Jacob Sanford?

Thomas Jacob Sanford lived in Burton, Michigan, just miles from the church where the attack occured. He served in the U.S. Marine Corps from 2004 to 2008, including a stint in the Middle East, and was awarded several medals and commendations.

Grand Blanc Township Police Chief William Renye said Sanford had previously been arrested on charges including burglary and operating a vehicle while intoxicated. It's unclear when the arrests happened.

Gunman allegedly expressed anti-Mormon bigotry

About a week before the shooting, he expressed distain toward the church and called Mormons "the Antichrist," according to Kris Johns, a candidate for the local Burton City Council.

Johns was canvassing when he knocked on Sanford's door and the two men discussed religion, Sanford's time in the military, their children and battles with addiction.

“It was very much standard anti-LDS talking points that you would find on YouTube, TikTok, Facebook," said Johns, adding that he has spoken with local police and the FBI about the encounter.

This story has been updated to add new information.

Contributing: John Wisely, Andrea May Sahouri and Clara Hendrickson, Detroit Free Press

This article originally appeared on USA TODAY: Investigators probe for motive in Michigan church shooting

Reporting by Jeanine Santucci and Christopher Cann, USA TODAY / USA TODAY

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