The ex-Marine responsible for fatally shooting four people at a Mormon church over the weekend had developed an intense grudge against the Church of Jesus Christ of Latter-day Saints as he fell into severe drug addiction.

Thomas Jacob Sanford, aged 40 and hailing from Burton, drove his pickup truck into the Grand Blanc Township church on Sunday morning, later starting a fire and engaging in gunfire.

of Burton, rammed his pickup truck into the Grand Blanc Township church on Sunday morning before opening fire and setting it ablaze.

He killed four people and injured eight others in the attack before he was gunned down by police.

According to those acquainted with Sanford, he harbored a profound animosity towards Mormons after a breakup with a religious partner in Utah more than a decade ago.

Peter Tersigni, a lifelong friend since preschool who considers Sanford his best friend, informed The New York Times that Sanford’s four-year tenure in the Marine Corps—including service in Iraq—transformed him from a class clown into a more somber individual.

His time living in Utah, combined with heavy methamphetamine use, changed his best friend even further, Tersigni and others said.

Sandra Winter, aged 56, who provided lodging to Sanford in Utah, recounted how he felt compelled to join the Church of Jesus Christ of Latter-day Saints due to his girlfriend’s influence.

‘He wasn’t so sure that he wanted to be a member of the church, but he really wanted to be with this woman,’ she said.

 It is unclear why Sanford broke up with the Mormon woman, but by the time he returned to Michigan ‘mentally he was in rough shape,’ Peter said. 

‘He got this whole fascination with Mormons and “they are the Antichrist and they are going to take over the world,”‘ Peter’s twin brother, Francis, explained.

The topic had become such an obsession for Sanford, that he even brought it up at Peter’s wedding, the brother’s said.

‘All he could talk about was Mormons,’ Peter recounted. ‘I was like, “Dude, nobody wants to hear about this stuff.”‘ 

But Sanford was not afraid to share his hatred, even telling a local politician canvassing his neighborhood last week that Mormons are the ‘Antichrist.’

Kris Johns, a resident running for city council, told the Detroit Free Press how Sanford shared his struggles with drug addiction following his time in the service – before asking him whether he believed in God.

Johns, a Christian who is a member of the Solid Rock Community Church in Burton, replied ‘yes’ to Sandford, adding: ‘From there, the conversation takes a very sharp turn.’ 

He was then asked by Sanford about the Mormon bible, the role Jesus plays in the religion, the history of the LDS church, and more, Johns said. 

‘I just didn’t know what the next question was going to be,’ he added. 

‘There’s certain things you don’t forget. This is not a forgettable guy.

‘It was very much standard anti-LDS talking points that you would find on YouTube, TikTok, Facebook,’ Johns said of Burton.

As he went on to speak of the religion, Sanford told Johns that he had his tattoos removed so he could take part in church ceremonies. 

Several inkings were seen on his arm in Facebook photos of Sanford, including barbed wire imagery and what appears to be a dreamcatcher. 

Yet Johns said he didn’t feel unsafe while speaking to Sanford.

‘It wasn’t anything I thought I needed to call police about. You hear all kinds of views these days. Nothing about it suggested he was going to hurt anyone.’ 

The Tersignis also said they were baffled when they learned Sanford was the gunman.

They had thought he had moved on from his heartbreak in Utah, as he was now married and was caring for his child, who had a rare genetic condition.

‘I can’t see him pulling the trigger and shooting people,’ Peter said. ‘I’m in disbelief.’

Authorities say Sanford opened fire at the Mormon church after ramming his car into the side of the building and set fire to the structure at around 10.25am on Sunday, while hundreds of people were in the building in Grand Blanc Township, outside Flint.

He 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.

As he gunned down the victims, he reportedly asked congregants whether they believed in Jesus as some Christians view Mormons as heretics.

 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. 

But officials say they are still working to determine a motive for the attack, calling the incident an ‘act of violence.’