A former United States Marine has been identified as the gunman who opened fire on a Mormon church in Michigan, killing at least four people and wounding several others.

Hundreds of worshippers were inside the Church of Latter Day Saints for the Sunday morning service, when 40-year-old Thomas Jacob Sanford rammed his truck through the entrance, opened fire with an assault rifle, and then used an accelerant to set the building on fire.

He was shot dead by police, while the church was gutted by flames.

US President Donald Trump was quick to label it a targeted attack on Christians, writing on Truth Social, “This epidemic of violence in our country must end, immediately”.

A motive for the attack remains unclear, but it has been revealed Sanford served in the Marines, and was an Iraq War veteran.

Authorities say they are issuing search warrants on Sandford’s residence and triaging through phone records.