A survivor of the Michigan church shooting has shared heart-wrenching details about how the tragic event started — and how the congregation’s goodwill led to devastation.

Paul Kirby, a member of the church in Grand Blanc Township, described how a ‘loud boom’ was heard from the rear of the chapel as chaos unfolded around 10:30 am on Sunday.

He and others rushed to check on Thomas Jacob Sanford, 40, after he rammed his pickup truck into the building, believing it was a traffic accident. 

But as they approached the vehicle, Sanford pulled out a rifle and opened fire in an attack that killed four and injured eight more.

‘A group of us men decided to get up and investigate what had occurred, thinking perhaps someone had lost control and hit the building,’ Kirby recounted to CBS Mornings.

‘We didn’t think anything bad was going to happen,’ he added.

As shots rang out, Kirby sprinted back inside to find his family, but while running for his life a piece of shrapnel impaled his left leg and he saw a bullet hit a glass door just a foot away from him.

‘It was just so unexpected. Once I saw the gun and start hearing him start shooting it, it was just a lot of fear,’ he continued. 

Once he reached his wife and two children, the worshiper ran out of the building with them and others and loaded as many as he could into the family’s car. 

While he did so, Kirby recalled seeing two people lying on the ground, he told The New York Times. 

‘I was afraid they were going to start shooting cars as we were leaving,’ he said, adding that it was ‘the scaredest [sic] I’ve ever been.’  

Tony Deck, another concerned resident that was thrown off by all the sirens he heard racing past his house, drove to the scene to bring bottles of water he had in his car. 

But when he arrived, Deck, 56, was stunned to see the walls of the church burning down and tarps on the ground that appeared to be covering bodies, he told the Times. 

Debbie Horkey, another local who lives near the Mormon church, said all she heard that morning was a women ‘just yelling for help.’ 

A woman who got separated from her husband inside the church said the scene so was terrifying she thought she wasn’t going to make it out alive. 

‘I thought, “If I have to die, it’s OK”,’ Kristin Juarez, 54, said. ‘I feel good about where I am. And then I heard my husband’s voice, and he was calling for me.’ 

Her husband, John Juarez, reunited with her after he helped other carry a wounded person outside. 

When he got back inside, he saw another injured person, Mr Juarez described. 

‘I didn’t know what I could do for him. I couldn’t get him out on my own.’ 

Investigators are still searching for the killer’s motive. 

But earlier today, Kris Johns, a resident running for city council, said he had a dark conversation with Sanford while canvasing the neighborhood just days before the attack. 

During their interaction, Johns, 44, said the shooter called Mormons ‘the anti-Christ.’ 

The city council candidate said the topic change to religion made him want to end the conversation. 

‘He was extremely nice at first. He even talked about his child who had a serious medical concern,’ Johns told journalist Dave Bondy.

‘But when the conversation turned to religion, I just wanted to get off the door and away from him,’ he added.

At the time, Sanford lived in Utah – a state with close ties to Mormonism – and was in a relationship with a woman who was involved in the Church of Jesus Christ of Latter-day Saints, Johns claimed.

The surviving victims’ ages ranged from six to 78, Dr. Michael Danic, chief of staff at Henry Ford Genesys Hospital, told NBC News.

Five of them were treated for gunshot wounds and three others were treated for smoke inhalation. The child was stabilized and released, according to the doctor.

The attack occurred about 10.25am while hundreds of people were in the building in Grand Blanc Township, outside Flint.

The man got out of the pick-up with two American flags raised in the truck bed and started shooting, Police Chief William Renye told reporters.

The attacker apparently used gas to start the fire and also had explosive devices but it wasn’t clear if he used them, said James Dier, of the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Acting Special Agent in Charge of the Detroit FBI field office Reuben Coleman said during a press conference Monday afternoon that they are ‘continuing to work to determine a motive.’

They are currently calling the investigation and ‘act of violence,’ he said.

Authorities are looking into the improvised explosive devices that were uncovered at the scene, Deir said.