Investigators are searching for a motive after a gunman opened fire at a Mormon church in Michigan and set the building on fire, killing four people.

Officials stated the attack on the Church of Jesus Christ of Latter-day Saints in Grand Blanc, a town 60 miles (100km) northwest of Detroit, occurred during a Sunday service attended by hundreds.

The suspect, identified as Thomas Jacob Sanford, 40, from Burton, Michigan, was killed by police shortly after the shooting.

During a news conference, officials noted that the incident was a targeted act of violence, but have yet to determine Sanford's motive.

How the attack unfolded

Authorities have not identified the four victims of the shooting, nor the eight others injured, including one in critical condition. Michigan Governor Gretchen Whitmer has urged the public not to speculate on motives as the investigation is ongoing.

The shooting began around 10:30 EST (15:30 BST) when the gunman crashed his vehicle into the church, followed by opening fire on congregants.

A churchgoer reported hearing a loud noise before seeing the attacker shooting from outside. It was just so unexpected, said Paul Kirby. Once I saw the gun, it was just a lot of fear.

After the shooting, the gunman ignited the church with gasoline or another accelerant. Authorities also discovered improvised explosive devices at the scene.

Less than ten minutes after the attack, the gunman died in a confrontation with police. Investigators have interviewed over 100 witnesses as part of their inquiry.

What we know about the suspect

Though officials have not clarified a motive, White House press secretary Karoline Leavitt informed Fox News that Sanford harbored animosity towards the Mormon faith.

Sanford, a former Marine who served in Iraq, had a history of arrests for burglary and driving under the influence. Limited information exists on his political views, though his social media activity indicates support for Donald Trump.

Sanford is believed to have a son facing severe health challenges, as noted in family posts and a fundraising effort. He lived in a suburb of Flint, near Grand Blanc Township.