SUTHERLAND SPRINGS, Texas (AP) — The gunman who opened fire in a small Texas church, killing 26 people during Sunday services, had sent threatening text messages to his mother-in-law before the attack, which appeared to stem from a domestic situation, authorities said Monday. 

Investigators have concluded that the massacre was not racially or religiously motivated, Texas Department of Public Safety Regional Director Freeman Martin said.

Based on evidence at the scene, they believe that Devin Patrick Kelley died of a self-inflicted gunshot wound after he crashed his car. He had been chased by armed bystanders.

The 26-year-old shooter also used his cellphone to tell his father that he had been shot and did not think he would survive, authorities said.

Once the shooting started at the First Baptist Church in Sutherland Springs, there was probably "no way" for congregants to escape, Wilson County Sheriff Joe D. Tackitt Jr. said.

The gunman, dressed in black tactical gear, fired an assault rifle as he walked down the center aisle during worship services. He turned around and continued shooting on his way out of the building, Tackitt said.

The gunman also carried a handgun, but authorities he did not know if it was fired. The attack claimed multiple members of some families and tore apart a close-knit town of 400 people.

"It's unbelievable to see children, men and women, laying there. Defenseless people," Tackitt said.

The dead ranged in age from 5 to 72 years old. About 20 other people were wounded.

Authorities said Kelley lived in New Braunfels, about 35 miles north of the Sutherland Springs church.

A U.S. official told The Associated Press that Kelley did not appear to be linked to organized terrorist groups. The official spoke on the condition of anonymity because the person wasn't authorized to discuss the investigation.

Investigators were looking at social media posts Kelley made in the days before the attack, including one that appeared to show an AR-15 semi-automatic weapon.

Kelley received a bad conduct discharge from the Air Force for assaulting his spouse and child and was sentenced to 12 months of confinement after a 2012 court-martial. Kelley served in Logistics Readiness at Holloman Air Force Base in New Mexico from 2010 until his 2014 discharge, Air Force spokeswoman Ann Stefanek said.

The attacker pulled into a gas station across from the church, about 30 miles southeast of San Antonio, around 11:20 a.m. Sunday. He crossed the street and started firing the rifle at the church, then continued firing after entering the white wood-frame building, said Freeman Martin, a regional director of the Texas Department of Safety.

As he left, the shooter was confronted by an armed resident who "grabbed his rifle and engaged that suspect," Martin said. A short time later, the suspect was found dead in his vehicle at the county line.

Twenty-three of the dead were found in the church, two were found outside and one died after being taken to a hospital, Martin said.

The man who confronted Kelley had help from another local resident, Johnnie Langendorff, who told KSAT-TV that he was driving past the church as the shooting happened. He didn't identify the armed resident but said the man exchanged gunfire with the gunman, then asked to get in Langendorff's truck and the pair followed as the gunman drove away.

Langendorff said the gunman eventually lost control of his vehicle and crashed. He said the other man walked up to the vehicle with his gun drawn and the suspect did not move. He stayed there for at least five minutes, until police arrived.

"I was strictly just acting on what's the right thing to do," Langendorff said.

Among those killed was the church pastor's 14-year-old daughter, Annabelle Pomeroy. Pastor Frank Pomeroy and his wife, Sherri, were both out of town when the attack occurred, Sherri Pomeroy wrote in a text message.

"We lost our 14-year-old daughter today and many friends," she wrote. "Neither of us has made it back into town yet to personally see the devastation."

Church member Nick Uhlig, 34, who was not at Sunday's service, told the AP that his cousin, who was eight months' pregnant, and her in-laws were among those killed. He later told the Houston Chronicle that three of his cousin's children also were slain.

President Donald Trump, who was in Japan, called the shooting an "act of evil," later calling the gunman "a very deranged individual."

On Sunday evening, two sheriff's vans were parked outside the gate of a cattle fence surrounding the address listed for Kelley on the rural outskirts of New Braunfels, north of San Antonio.

Ryan Albers, 16, who lives across the road, said he heard intensifying gunfire coming from that direction in recent days.

"It was definitely not just a shotgun or someone hunting," Albers said.

The church has posted videos of its Sunday services on a YouTube channel, raising the possibility that the shooting was captured on video.

In a video of its Oct. 8 service, a congregant who spoke and read Scripture pointed to the Oct. 1 Las Vegas shooting a week earlier as evidence of the "wicked nature" of man. That shooting left 58 dead and more than 500 injured.

Gov. Greg Abbott called Sunday's attack the worst mass shooting in Texas history. It came on the eighth anniversary of a shooting at Fort Hood, where 13 people were killed and 31 others wounded by a former Army major.

The previous deadliest mass shooting in Texas had been a 1991 attack in Killeen, when a mentally disturbed man crashed his pickup truck through a restaurant window at lunchtime and started shooting people, killing 23 and injuring more than 20 others.

The University of Texas was the site of one of the most infamous mass shootings in American history, when Marine sniper Charles Whitman climbed the Austin campus' clock tower in 1966 and began firing on stunned people below, killing 13 and wounding nearly three dozen others. He had killed his wife and mother before heading to the tower. One victim died a week later, and medical examiners eventually attributed a 17th death to Whitman in 2001.

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Associated Press writers Sadie Gurman and Eric Tucker in Washington, Nomaan Merchant in Houston, Will Weissert in Austin, Diana Heidgerd in Dallas, Michael Balsamo in Los Angeles and Paul J. Weber in New Braunfels, Texas, contributed to this report.

House of worship shootings

Some fatal shootings that have happened at U.S. houses of worship since 2012:

Nov. 5, 2017: Dressed in black tactical-style gear and armed with an assault weapon, 26-year-old Devin Kelley opened fire at the First Baptist Church of Sutherland Springs, Texas, killing 26 people and wounding about 20 others.

Sept 24, 2017: Emanuel Kidega Samson, 25, was charged with killing a woman and wounding six other people with gunshots at Burnette Chapel Church of Christ in Nashville, Tennessee.

Aug. 13, 2016: Imam Maulana Alauddin Akonjee and his friend Thara Uddin were fatally shot as they left a New York City mosque. Oscar Morel, 35, was charged with second-degree murder.

Aug. 9, 2016: A shooting during a party at a Jersey City, New Jersey, church left 17-year-old Leander Williams dead and two teenage girls wounded. Daequan Jackson, 18, was charged with murder.

April 24, 2016: Mark Storms fatally shot 27-year-old Robert Braxton III during Sunday services in a suburban Philadelphia church. Storms, 46, argued self-defense, but was sentenced to 10 to 20 years in prison for voluntary manslaughter.

Feb. 28, 2016: Rev. William B. Schooler, 70, was fatally shot by his 68-year-old brother inside an office at St. Peter's Missionary Baptist Church in Dayton, Ohio, as Sunday services were winding down. Daniel Schooler was found guilty of murder and sentenced to 31 years to life in prison.

June 17, 2015: Nine black worshippers including a pastor were killed by Dylann Roof, a 21-year-old white supremacist, after he prayed with them for nearly an hour. The shooting happened at historic Emanuel African Methodist Episcopal Church in downtown Charleston, South Carolina. Roof was convicted of federal hate-crime and obstruction-of-religion charges and sentenced to death.

April 13, 2014: Neo-Nazi and former Ku Klux Klan leader Frazier Miller Jr. fatally shot Dr. William Corporon and his 14-year-old grandson Reat Underwood outside an Overland Park, Kansas, Jewish center as they arrived for a community event. He then drove to a Jewish retirement community where he fatally shot Terry LaManno, who was visiting her mother.

March 31, 2013: A 28-year-old man fatally shot his father during Easter services at the Hiawatha Church of God in Christ in Ashtabula, Ohio. Reshad Riddle then made a rambling statement at the pulpit while yelling about God and Allah, still holding his handgun as panicked worshippers fled the church.

Dec. 2, 2012: Elementary school music teacher Gregory Eldred, 52, shot his ex-wife, Darlene Sitler, while she played the organ during a church service at the First United Presbyterian Church in Coudersport, Pennsylvania.

Oct. 24, 2012: A former facilities maintenance employee at World Changers Church International in College Park, Georgia, opened fire, killing church volunteer Greg McDowell, 39, while he was leading a prayer. Police arrested Floyd Palmer, 51, who was found guilty but mentally ill and sentenced to life in prison.

Aug. 5, 2012: Six members of the Sikh Temple of Wisconsin, in Oak Creek, were fatally shot by a white supremacist, Wade Michael Page. Page was shot by a responding officer and later killed himself.

May 9, 2012: Joseph Lewis Jr., 84, was fatally shot while sitting in a car guarding Victory Way Assembly Church of God in Christ in Detroit, Michigan. Two teenagers, 15-year-old Anthony Williams and 18-year-old Alandre Boone, attacked him while a Bible study took place inside. Police suspected robbery was the motive. Both teenagers were tried and convicted as adults for second-degree murder.

May 3, 2012: A homeless man killed himself after fatally shooting a priest and a church secretary at St. Peter's Episcopal Church in Ellicott City, Maryland. Police said Douglas Franklin Jones had been turned away from the church food bank about two weeks earlier for visiting every day instead of weekly.

Source: News reports