Police said the perpetrator, identified as Thomas Jacob Sanford, 40, a former US Marine from the nearby town of Burton, also deliberately set fire to the church, which was engulfed in flames and billowing smoke.
"We do believe that we will find some additional victims once we find the area where the fire was," Grand Blanc Township Police Chief William Renye told a press conference.
Hundreds of people were in the church on Sunday when Sanford drove into the building, Renye said.
Two law enforcement officers, one from the state Department of Natural Resources and another from Grand Blanc Township, rushed to the scene and engaged the suspect in an exchange of gunfire, shooting him dead, Renye said.
Investigators will search the shooter's home and phone records in search of a motive, Renye said.
US military records show Sanford was a US Marine from 2004 to 2008 and an Iraq war veteran.
Coincidentally, another 40-year-old Marine veteran who served in Iraq is a suspect in a North Carolina shooting that killed three people and wounded five others less than 14 hours before the Michigan incident.
Police in Southport, North Carolina, accused Nigel Max Edge of firing on a waterfront bar from a boat on Saturday night. Edge has been charged with three counts of first-degree murder and five counts of attempted murder, police said.
According to court records, a federal lawsuit that Edge had filed against the US government, and others, describe him as a decorated Marine who suffered severe wounds including traumatic brain injury in Iraq. The lawsuit, which was dismissed, showed Edge was previously known as Sean William DeBevoise before changing his name.
In Michigan, a woman who gave her name as Paula described her escape as "surreal" in an interview with WXYZ television.
"We heard a big bang and the doors blew. And then everybody rushed out," she said, adding that there was no security and the shooter opened fire on parishioners as they fled.
"I lost friends in there and some of my little primary children that I teach on Sundays were hurt. It's very devastating for me," she said.
The Mormons, formally known as the Church of Jesus Christ of Latter-day Saints, follow the teachings of Jesus but also the prophecies of Joseph Smith, a 19th century American.
Grand Blanc, a town of 7700 people, is about 100km northwest of Detroit.
"My heart is breaking for the Grand Blanc community," Michigan Governor Gretchen Whitmer said in a statement posted to social media.
"Violence anywhere especially in a place of worship, is unacceptable."
President Donald Trump in a statement on Truth Social said that the shooting "appears to be yet another targeted attack on Christians in the United States of America" and said the FBI was on the scene. "THIS EPIDEMIC OF VIOLENCE IN OUR COUNTRY MUST END, IMMEDIATELY!"
The Michigan rampage marked the 324th mass shooting in the US in 2025, according to the Gun Violence Archive, which tracks such incidents and describes a mass shooting as one in which four or more people are shot or killed, not including the shooter.
It was also the third US mass shooting in less than 24 hours, including the North Carolina incident and a shooting a few hours later at a casino in Eagle Pass, Texas, that killed at least two people and injured several others.
with AP
