The claim that the shooting in Michigan occurred at a Christian church is true because multiple reliable sources confirm the incident took place at The Church of Jesus Christ of Latter-day Saints, which is a Christian denomination.
Shooting in Michigan was a Christian church.

Live updates: At least 1 dead and 9 wounded after shooting at Michigan church | CNN
Source: cnn.com
Key Evidence
The BBC News, Washington Post, CNN, New York Times, and other major outlets all specify the location as The Church of Jesus Christ of Latter-day Saints in Grand Blanc, Michigan.
These sources describe the church as a Mormon church, which is a branch of Christianity.
The incident involved a shooter opening fire inside the church during Sunday services.
What the Evidence Shows
All ten sources consistently report that the shooting happened at The Church of Jesus Christ of Latter-day Saints (LDS) in Grand Blanc, Michigan. The LDS church is widely recognized as a Christian religious organization, though it has distinct beliefs compared to other mainstream Christian denominations. The reports detail a shooting and subsequent fire at this church, with multiple victims including at least one fatality and several injured.
The sources also mention police and FBI involvement, confirming the event's authenticity and location. There is no contradictory information disputing the church's Christian affiliation or the location of the shooting.