Smoke was billowing from the building as firefighters sprayed the blaze with water while fire trucks and emergency vehicles were parked nearby, footage on social media showed.
There are multiple victims and the shooter is down. There is no threat to the public at this time. The church is actively on fire," the Grand Blanc Township Police Department said in a post on Facebook, urging people to avoid the area.
Further details were not immediately available.
The Church of Jesus Christ of Latter-day Saints is informally known as the Mormons.
Grand Blanc, a town of 7,700 people, is located about 60 miles (97 km) northwest of Detroit.
Reporting by icelynbright247blog