Four people were killed and several others were wounded Sunday when, authorities say, a man opened fire at a Church of Jesus Christ of Latter-day Saints in Grand Blanc Township, Michigan, and set it ablaze in what a federal official called “an act of targeted violence.”

At least two of the four victims were fatally shot, police said. Five people were wounded by gunfire and three suffered smoke inhalation, said Dr. Michael Danic, the chief of staff at Henry Ford Genesys Hospital, where the injured were treated.

Two gunshot patients were in critical condition Monday, Danic said.

Authorities are searching through the debris of the church but on Monday morning said everyone had been accounted for.

The suspect, Thomas Jacob Sanford, 40, a former Marine, was killed by law enforcement.

Here is what we know about the shooting.

How the attack unfolded

At 10:25 a.m. Sunday, a gunman drove a vehicle into the church, got out and opened fire with an assault rifle, township Police Chief Bill Renye said.

The first officers arrived within 30 seconds of initial reports, and law enforcement killed the shooter in the rear parking lot eight minutes after the first reports, he said.

Authorities believe the shooter was able to spark a fire that eventually enveloped the church before it was contained, Renye said.

Paula Maser was among the worshippers in the church for a Sunday service.

“We heard a big bang and it blew the doors in the church, and then everything after that was chaos,” Maser told NBC affiliate WEYI of Flint, Michigan.

Maser said she and others ran outside, where she and a friend got into a car. The gunman also went outside, Maser said, and continued to fire. Three bullets struck the car Maser was in, she said, one of which grazed her friend’s hand.

Janet Peera, who lives nearby, told the station that she and her family were leaving their home when they saw police vehicles and fire trucks racing toward the scene and heard gunshots.

Amid the chaos, Peera said, the family ended up in the church parking lot.

“There were bodies lying on the sidewalk,” she said. “There was one lying in the back of somebody’s truck that had just gotten shot maybe a couple times in the leg.”

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Where the investigation stands

It’s not clear what motivated the shooting, and officials did not disclose whether there was any known connection between the suspect and the church.

The FBI is investigating the incident as “an act of targeted violence,” Reuben Coleman, the acting special agent in charge of the bureau’s Detroit field office, said at a news conference Sunday night.

“This act of violence has no place in our state or anywhere else in our country,” Coleman said. “The FBI is committed to continue finding out the facts, circumstances and motives behind this tragedy.”

More than 100 witnesses have been interviewed, Coleman said Monday, with more interviews still to be done.

The Bureau of Alcohol, Tobacco, Firearms and Explosives is also aiding in the investigation. James Deir, special agent in charge of the ATF in Detroit, said the investigation indicates the suspect used an accelerant, believed to be gasoline, to set the blaze. He also said that “suspected explosive devices” were found at the site but that it is not clear whether they sparked the inferno.

Renye said the church is a “total loss” as a result of the fire.

None of the victims had been identified as of Monday night, and officials said first responders are in “recovery mode,” sifting through debris for additional bodies and evidence.

What we know about the suspect

Sanford, of Burton — a city roughly 6 miles from Grand Blanc Township — had a military background.

His father, Thomas Sanford, speaking on behalf of the suspect’s family, said in a statement Monday that close relatives are “completely in shock” and “have no answers” regarding a possible motive.

“We are devastated,” Thomas Sanford said. “Our hearts and prayers go out to the Grand Blanc community and all those affected by this tragedy. Our son was a Christian and a loving father, son, and husband.”

Sanford joined the Marine Corps in 2004 and held the titles of organizational automotive mechanic and vehicle recovery operator, according to Marine records.

His service included a deployment from August 2007 to March 2008 under Operation Iraqi Freedom, according to the Marines.

He had become a sergeant and had his last duty assignment at Camp Lejeune, North Carolina, according to the Marines. He left the military in June 2008, according to the records.

Awards for his service include the Marine Corps Good Conduct Medal, the Sea Service Deployment Ribbon, the Iraq Campaign Medal, the Global War on Terrorism Service Medal and the National Defense Service Medal, the records show.

A 2007 story in the Clarkston News said Sanford graduated in 2003 from nearby Goodrich High School and was soon to be deployed to Fallujah, Iraq. Superintendent Mike Baszler of Goodrich Area Schools, which canceled instruction Monday, said he graduated from the district in 2004.