Far below the towering and piercing spires atop every Church of Jesus Christ of Latter-day Saints chapel, a small sign beckoning visitors can be found.

“Visitors welcome” signage is part of the uniform for meeting houses, standardized by the LDS church’s governing voices in Salt Lake City, serving as a testament to the faith’s robust evangelizing efforts.

But on Sunday morning, one visitor took advantage of the church’s open arms, ramming his truck into a chapel in Grand Blanc, Michigan, then set it on fire, shooting at worshippers before dying in a shootout with police.

At least four people were killed, and eight others were wounded. More are still unaccounted for.

The chapel on McCandlish Road is the latest place of worship to be devastated by unrelenting gun violence, and the FBI is now leading the investigation into the attack as an act of targeted violence, authorities said Sunday.

The chapel joins, among others, a Minneapolis Catholic church, Pittsburgh synagogue and Sikh temple where people — both young and old — were killed.

They were gathering for different reasons — to celebrate the start of a new school year, to mourn the loss of a church leader or for a Bible study. Many were praying.

Timothy Jones, who belongs to an LDS congregation 15 minutes away from Grand Blanc, told the Associated Press Sundays are “supposed to be a time of peace and a time of reflection and worship.”

But in the wake of violence at houses of worship, a shooting “feels inevitable, and all the more tragic because of that,” he said.

The day of the shooting was on what the Church calls a “fast Sunday,” a time once a month where members globally are encouraged to fast for two meals and donate the food, or the money they would have spent on food, to the poor. Fasting is also a common practice in LDS faith during grieving.

“This is a Sunday in which members of the church are being told to think of other people, to be charitable, to be kind, to reach out and give,” said Matthew Bowman, professor of history and religion at Claremont Graduate University. “It’s kind of a terrible irony, what happened on that day.”

Grief was already visiting the Church of Jesus Christ of Latter-day Saints ahead of Sunday’s attack. Its leader — President Russell M. Nelson — had died the day before. Hundreds, dressed in their Sunday best, and many likely fasting, congregated in Grand Blanc for the weekly 10 a.m. service.

Just 20 minutes later, the mood would shift from somber to horror and chaos as the gunman rammed his four-door pickup into the front of the chapel. Two American flags sat straight up against the back window in the truck’s bed.

Worshippers had just finished the Sacrament, the first half of the two-hour long service, said Paula, a woman who was at the church house and was interviewed by CNN affiliate WXYZ. She and another churchgoer were helping a woman into the car when the shooter started firing.

“We heard a big bang and the doors flew open,” Paula said.

Police said the 40-year-old suspect, Thomas Jacob Sanford, fired several rounds from an assault weapon at the worshippers.

Brian, another churchgoer whose button-down shirt had been stained with blood, told WXYZ he was trying to help some of the elderly ladies into his car when he was injured. His right hand, wrapped in gauze, was likely injured when the gunman opened fire on their vehicle, he said.

“We were trying to gather as many people as we could,” Brian said. “I saw the active shooter come out of the building, and at that point, I just started trying to drive away,” he said.

Paula couldn’t see the shooter, she said, and didn’t know whether he had entered the church.

“I didn’t know if we had to get down, because we couldn’t see anybody,” she said, calling the moment surreal.

Churchgoers also rushed to protect children, Grand Blanc Township Police Chief William Renye said at a news conference Sunday.

“They were shielding the children who are also present within the church, moving them to safety,” he said.

Some of the primary children she taught on Sundays, Paula said, were hurt. She said she joined the Grand Blanc church — the same building attacked on Sunday — 38 years ago. That morning, she had picked up a friend for church service and chatted with others inside before the shots rang out.

“It’s devastating to know I lost friends,” she said, her voice breaking.

The Grand Blanc chapel sits on McCandlish Road, a quiet stretch dotted with houses near a sprawling golf course and lake. A parking lot and large lawn surround the red brick meeting house, where its lone, white spire had loomed large.

Scores of emergency sirens reverberated along the hushed road Sunday morning as police officers responded to the scene less than 30 seconds after the first call to 911, Renye said.

As the suspect fled the church, two officers pursued him and “engaged in gunfire,” the police chief said. He was killed in the parking lot eight minutes after police arrived.

Responders’ full attention turned to rescuing victims.

Firefighters battled the blaze and the thick clouds of smoke for hours as people behind the police cordon looked on in disbelief. Survivors gathered at the reunification center and hugged each other in tears.

Authorities are still combing through debris and “working tirelessly to find additional bodies,” Renye said Sunday evening, unable to define how many people are still missing.

Up to seven people were possibly still unaccounted for as authorities concluded search efforts for the night late Sunday, a law enforcement source familiar with the investigation told CNN.

When striking nurses at nearby Henry Ford Genesys Hospital heard about the shooting, some left the picket line and ran the short distance to the church to help first responders, Teamsters Local 332 President Dan Glass said.

“Human lives matter more than our labor dispute,” Glass said.

Brian, the churchgoer, said he’s worried about his fellow worshippers.

“We don’t know the status of them,” he said.

The police chief said they believe some victims were “near the fire and they were unable to get out of the church.”

Cindy Walsh, who lives near the chapel, was at home watching TV when she heard the gunshots and came outside to investigate.

“All of a sudden, I saw smoke coming out and then people were coming out,” she told WXYZ.

The blaze moved rapidly, engulfing the chapel and sending massive plumes of thick, black smoke across the sky. The destruction was evident from the road which was cordoned off.

Details around the blaze are still being investigated. Authorities are “trying to determine exactly when and where that fire ended up coming from and how it got started,” though they believe the suspect started the fire “deliberately,” Renye added.

Sanford used an accelerant, like gasoline, police believe, to light the church on fire, said James Deir, special agent in charge of the Detroit field division of the Bureau of Alcohol, Tobacco, Firearms and Explosives. Evidence technicians went to process the scene after the fire was extinguished, and investigators said they found “some suspected explosive devices.”

“I’m shaken, I’m very shaken,” Walsh said. “I’ve seen a change in this world, there’s so much hate in this world, I just don’t understand it.”

The chapel, once bathed in sunlight and surrounded by greenery, is now unrecognizable. The building is a “total loss,” Renye said.

Debris piles have replaced pews; the welcoming meeting house has closed its doors; and the LDS church’s mounting grief has swelled.

And the tall white spire, which once towered over Grand Blanc worshippers as it reached toward heaven, is gone.

CNN’s Josh Campbell contributed to this report.