Members of The Church of Jesus Christ of Latter-day Saints in Grand Blanc, Michigan, were about a half hour into their Sunday morning service when they described hearing a "big bang" followed by gunfire.
A 40-year-old man wielding an assault rifle rammed his pickup truck through the front doors of the church and opened fire on "hundreds of people" at the service, seemingly shooting people indiscriminately inside the chapel, according to police.
At least 10 people were shot in the attack, including two who died, police said. The suspect, whose name was not released, was killed in a gunfight with police after he allegedly set the church on fire, authorities said.
A Sunday school teacher at the church, who only wanted to be identified by her first name Paula, described the chaos as congregants went from singing religious songs to running and diving for cover.
"We heard a big bang and the doors blew," Paula told ABC affiliate station WXYZ in Detroit.
Paula said people attending the service started to rush out of the church and tried to run to their cars.
Grand Blanc Police Chief William Renye said at a news conference that the suspect lived in Burton, about 8 miles north of Grand Blanc.
The chief said that at least two victims were in critical condition. "We do believe we will find additional victims once we have that scene secured," Renye said.
Paula told WXYZ there's no security at the church.
"I didn't know what was going on and I didn't know if we were going to have to get down because we couldn't see anybody. We couldn't see," Paula said, adding that she didn't see the shooter.
"My church is gone. I joined the church 38 years ago in that building and now it's gone," Paula said. "It's devastating to know that I've lost friends and to see somebody would do this to our church."
Church of Jesus Christ of Latter-day Saints spokesperson Doug Anderson issued a statement, confirming that the attack occurred during a church service.
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Anderson said the Church is in communication with local law enforcement as the investigation continues.
"We offer thanks to the emergency responders who are assisting victims and families," Anderson said. "Places of worship are meant to be sanctuaries of peacemaking, prayer and connection. We pray for peace and healing for all involved."