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The gunman behind the worst shooting in Texas history — officially identified Monday as 26-year-old Devin Patrick Kelley — didn't have a license to carry a gun, state officials said.

Devin Kelley (Texas Department of Public Safety)

Kelley put on a ballistic vest and donned a black mask with a white skull on it before killing 26 people with an assault rifle at a Sutherland Springs church Sunday morning.

Officials said the attack was recorded on video; the church regularly posted recordings of its services on Youtube.

At a news conference, officials said Kelley had threatened his mother-in-law, who attended the church.

"There was a domestic situation going on within this family," said Freeman Martin, Texas Department of Public Safety regional director. Kelley's mother-in-law "had received threatening texts from him."

Authorities said the attack was not motivated by race or religion.

Earlier Monday, Gov. Greg Abbott suggested that Kelley may have a connection to the Baptist church.

Abbott said on ABC's Good Morning America that "law enforcement is looking very aggressively into this."

Abbott called Kelley "a very deranged individual." The governor didn't go into further detail about his connection to the church, saying that "it's very important that law enforcement have the ability … to tie the loose ends of this investigation up."

The Texas Department of Public Safety said Kelley lived in New Braunfels, about 35 miles north of the Sutherland Springs church where the shooting occurred.

Claudia Varjabedian, a manager at the Summit Vacation Resort in New Braunfels, said Kelley had worked there as a security guard the past month and a half.

She says Kelley "seemed like a nice guy" and didn't give her any problems. She said he worked unarmed on his shift as the day security guard.

The riverside resort in the Texas Hill Country is near Kelley's apparent home off a rural highway. Sheriff's deputies were still blocking the gate to his property Monday morning.

Kelley had also worked briefly at the Schlitterbahn in New Braunfels as an unarmed security guard.

The amusement park said in a statement that he was fired in July after working there for five and a half weeks.

Kelley began shooting from outside Sutherland Springs' First Baptist Church before he entered the building to continue gunning down the congregation at the 11 a.m. service. His in-laws were members of the church but were not in attendance Sunday.

Kelley had been spotted about 11:20 a.m. at a gas station on the other side of U.S. Highway 87 before he drove up to the church about 35 miles from San Antonio.

Dressed in tactical gear, Kelley was armed with a Ruger assault-style rifle, authorities said. He fired on churchgoers as he walked down the aisle at the small building, then turned around and kept shooting as he walked back out.

His is Texas' worst mass shooting in modern history, surpassing the attack where 23 people were murdered and 20 more were wounded at a Killeen Luby's in 1991.

Once Kelley started shooting, there was probably "no way" for congregants at First Baptist to escape, Wilson County Sheriff Joe Tackitt said Monday.

As the gunman left the church, a town resident grabbed his own rifle and confronted him, Martin said. The gunman dropped his gun and fled in his vehicle, and the resident, Stephen Willeford, pursued him in the vehicle of passer-by Johnnie Langendorff.

Kelley was found dead in his vehicle, which had crashed near the Wilson and Guadalupe county lines.

Authorities recovered a Ruger AR-556 rifle at the church and two handguns — a Glock 9mm and a Ruger .22-caliber — from Kelley's vehicle, said Fred Milanowski, special agent in charge of the Bureau of Alcohol, Tobacco, Firearms and Explosive's Houston office.

Johnny Langendorff, who was one of the men who said they pursued Devin Kelly after a deadly church shooting, waits to be picked up from the scene where Kelley was found dead near the intersection of FM539 and Sandy Elm Road in Guadalupe County. (William Luther / San Antonio Express-News)

Martin said Monday that Kelley had called his father to say that he didn't think he'd live.

"The suspect used his cellphone, notified his father that he had been shot and didn't think he was going to make it," Martin said.

Martin said evidence at the scene indicated that Kelley had killed himself, but an autopsy will determine the official cause of death.

Willeford was not wounded in the exchange of gunfire outside the church.

Twenty-three of the victims died inside the church, two more were found dead outside and another died at a hospital, Martin said. About 20 people were taken to area hospitals — some of them with severe wounds.

Ten people remained hospitalized in critical condition Monday, Martin said.

Some people escaped the church without injuries, though it's unclear how many. Neighbors say about 50 people usually attend services there.

The victims, who range in age from 18 months to 77, have not been publicly identified. Tackitt said authorities were working to identify victims and begin notifying their families.

The bodies had all been removed from the church by Monday morning.

The church's pastor, Frank Pomeroy, told ABC News that his 14-year-old daughter, Annabelle, was among the dead. He had not attended the service Sunday because he was in Oklahoma.

A woman prays with a man after a fatal shooting at the First Baptist Church in Sutherland Springs on Sunday. (Nick Wagner / Austin American-Statesman)

Air Force spokeswoman Ann Stefanek confirmed Kelley began serving in logistics readiness at Holloman Air Force Base in New Mexico in 2010. He was responsible for moving passengers, cargo and personal property in military transportation.

Kelley served 12 months' confinement after a 2012 court-martial for assaulting his wife and stepson, Stefanek said.

The Air Force's chief prosecutor in the case, Don Christensen, told The New York Times that Kelley had fractured the boy's skull.

He ultimately received a bad-conduct discharge and reduction in rank.

Defense Department records indicate he left the military in May 2014.

Officials in Comal County said deputies were called to Kelley's home earlier that year after a report that he was abusing his girlfriend.

The people at the home told deputies that there was no problem, and they left. Kelley married his girlfriend two months later.

The Texas Department of Public Safety issued Kelley a private security license this year.

"The investigation is ongoing. We are unable to confirm any additional information about the shooting suspect at this time," DPS spokesman Tom Vinger said in an email.

Abbott told CNN that there are "more unknowns than knowns" as investigators continue looking into the shooting.

Abbott said Kelley applied for a gun license in the state of Texas and was denied.

"By all the facts that we seem to know, he was not supposed to have access to a gun, so how did this happen?" Abbott said.

1 / 17The investigation continues at the First Baptist Church of Sutherland Springs.(Louis DeLuca / Staff Photographer) 2 / 17Texas State Trooper John Henke visits with a kitten who wanders by the blockade on the road outside the First Baptist Church of Sutherland Springs.(Louis DeLuca / Staff Photographer) 3 / 17A look at the community building near the First Baptist Church.(Louis DeLuca / Staff Photographer) 4 / 17As members of the media record the scene, a resident of Sutherland Springs surveys the situation from his porch.(Louis DeLuca / Staff Photographer) 5 / 17A state trooper directs traffic at the intersection near the First Baptist Church.(Louis DeLuca / Staff Photographer) 6 / 17Media gathers at the intersection near the First Baptist Church.(Louis DeLuca / Staff Photographer) 7 / 17The investigation continues at the First Baptist Church of Sutherland Springs.(Louis DeLuca / Staff Photographer) 8 / 17The investigation continues at the First Baptist Church of Sutherland Springs.(Louis DeLuca / Staff Photographer) 9 / 17Media gathers at the intersection near the First Baptist Church.(Louis DeLuca / Staff Photographer) 10 / 17Sutherland Springs resident David Casillas talks with the media.(Louis DeLuca / Staff Photographer) 11 / 17People pray in a field near the First Baptist Church of Sutherland Springs.(Louis DeLuca / Staff Photographer) 12 / 17A team of FBI personnel walks the adjacent property looking for evidence.(Louis DeLuca / Staff Photographer) 13 / 17Sheree Rumph of San Antonio prays over 26 crosses that were placed near Highway 87 just down the block from First Baptist Church in Sutherland Springs.(Louis DeLuca / Staff Photographer) 14 / 17Michelle Trigo, left, and Malinda Lamford of San Antonio deliver 26 balloons, flowers, and a stuffed teddy bear to the First Baptist Church of Sutherland Springs.(Louis DeLuca / Staff Photographer) 15 / 17Malinda Lamford, left, and Michelle Trigo release 26 balloons in tribute to those killed at the First Baptist Church.(Louis DeLuca / Staff Photographer) 16 / 17Michelle Trigo, left ,and Malinda Lamford of San Antonio deliver 26 balloons, flowers, and a stuffed teddy bear to the First Baptist Church of Sutherland Springs.(Louis DeLuca / Staff Photographer) 17 / 17Michelle Trigo, right, and Malinda Lamford of San Antonio deliver 26 balloons, flowers, and a stuffed teddy bear to the First Baptist Church of Sutherland Springs.(Louis DeLuca / Staff Photographer)

A federal official said Kelley didn’t appear to be linked to an organized terrorist group.

The official said investigators are looking at social-media posts Kelley may have made in the days before Sunday's attack, including one that appeared to show an AR-15 semiautomatic weapon.

A person with Kelley's name and date of birth registered in 2014 to vote in Colorado, with an address listed in Colorado Springs, home of the U.S. Air Force Academy. The registration is now inactive.

In 2014, he was arrested on an animal-cruelty charge in Colorado Springs after witnesses reported seeing him beat a husky and drag it by its neck. The charge was dismissed after Kelley completed deferred-adjudication probation.

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Authorities were at a home Sunday night in New Braunfels that has been identified as Kelley's. State troopers and a Comal County Sheriff's Office vehicle blocked the gate that opens up to the large family property in a rural part of the city.

People who live near the home north of San Antonio said they had heard intense gunfire from its vicinity in recent days.

Several neighbors also said that in recent weeks someone at the residence had been leaving expensive items, including couches, recliners and bicycles at the curb.

Mark Morovitz, 41, lives across the road from the Kelley residence and used to do work for Micky Kelley, Devin Kelley's father, until the two had a falling out two years ago. He said he had met Devin Kelley but didn't know him well.

He said his neighbors kept mostly to themselves but he and his family often heard gunfire — including what they though were shotguns and rapid-fire rifles — echoing from the property at night.

"That wouldn't have ever struck me as suspicious," Morovitz said. "Until now."

1 / 12Law enforcement officials enter the property of Devin P. Kelley on November 5, 2017 near New Braunfels, Texas. According to reports, Kelley, 26, entered a church during a service and opened fire, killing 26 people and injuring at least 20. (Erich Schlegel / Getty Images) 2 / 12Law enforcement officials works at the scene of a fatal shooting at the First Baptist Church in Sutherland Springs, Texas, on Sunday, Nov. 5, 2017.(Nick Wagner / Austin American-Statesman) 3 / 12Investigators work at the scene of a deadly shooting at the First Baptist Church in Sutherland Springs, Texas, Sunday Nov. 5, 2017. (Jay Janner / Austin American-Statesman) 4 / 12Texas Gov. Greg Abbott arrives to the Stockdale Community Center to address members of the media about a deadly shooting at the First Baptist Church in Sutherland Springs, during a press conference in Stockdale, Texas, Sunday, Nov. 5, 2017. (Nick Wagner / Austin American-Statesman) 5 / 12People comfort each other at a community center near the scene of a deadly shooting at the First Baptist Church in Sutherland Springs, Texas, Sunday, Nov. 5, 2017.(Jay Janner / Austin American-Statesman) 6 / 12Law enforcement officials gather near the First Baptist Church following a shooting on November 5, 2017 in Sutherland Springs, Texas.(Erich Schlegel / Getty Images) 7 / 12Law enforcement officials gather near the First Baptist Church following a shooting on November 5, 2017 in Sutherland Springs, Texas. (Erich Schlegel / Getty Images) 8 / 12A man wipes his eyes after a deadly shooting at the First Baptist Church in Sutherland Springs, Texas, Sunday, Nov. 5, 2017. (Nick Wagner / Austin American-Statesman) 9 / 12People gather near First Baptist Church following a shooting on November 5, 2017 in Sutherland Springs, Texas. (Erich Schlegel / Getty Images) 10 / 12Enrique and Gabby Garcia watch investigators at the scene of a mass shooting at the First Baptist Church in Sutherland Springs, Texas, on Sunday Nov. 5, 2017. (Jay Janner / Austin American-Statesman) 11 / 12A couple comfort each other at a community center in Sutherland Springs, Texas, near the scene of a mass shooting at the First Baptist Church on Sunday, Nov. 5, 2017.(Jay Janner / Austin American-Statesman) 12 / 12People hug outside Connally Memorial Medical Center in Floresville, Texas, Sunday, Nov. 5, 2017. A man opened fire inside of the First Baptist Church in Sutherland Springs, Texas, Sunday, killing more than 20 people. (William Luther / San Antonio Express-News)

Gov. Greg Abbott said the tragedy is "worsened" by the fact that it occurred in a church.

"As a state we are dealing with the largest mass shooting in our states' history," he said. "There are so many families that have lost family members, fathers, mothers, sons and daughters."

Our prayers are with all who were harmed by this evil act. Our thanks to law enforcement for their response. More details from DPS soon. https://t.co/KMCRmOPkiM — Greg Abbott (@GregAbbott_TX) November 5, 2017

U.S. Rep. Henry Cuellar, whose district includes the rural community of about 700 people, called the shooting "a horrific tragedy."

He said the town is "one of those unique communities where everyone knows everyone else and supports each other." He recalled fundraisers at the local fire department "where basically everyone in the entire area would come out to support those volunteers.

"The people of Sutherland Springs are as fine an example of Texans and Americans as you will find anywhere in the country," the Laredo Democrat said.

Governor Greg Abbott comforts a local resident during a candlelight vigil Sunday following the mass shooting inside the First Baptist Church in Sutherland Springs, Texas. (Suzanne Cordeiro / Agence France-Presse)

President Donald Trump called the deadly shooting an "act of evil."

Trump said he was monitoring the tragedy from Japan during his trip to five Asian countries.

"Our hearts are broken," he said. But he vowed Americans will pull together to help those who are suffering.

Vice President Mike Pence and his wife, Karen Pence, plan to travel to Sutherland Springs on Wednesday to meet with the victims' families as well as law-enforcement personnel.

Karen & I will travel to #SutherlandSprings on Wednesday to meet w/families of the fallen, injured & law enforcement. We are with you Texas — Vice President Mike Pence (@VP) November 6, 2017

The president said the mass shooting "isn't a guns situation." He called it a "mental-health problem at the highest level."

There have been no reports so far about details of Kelley's mental health. Abbott said, however, that mental health "is a very profound issue that our country must begin to address more profoundly."

Just spoke w/ @GregAbbott_TX about this horrific shooting. State & fed law enforcement working closely. Prayers for all harmed. Truly evil. https://t.co/VBRqjBkwx2 — Ted Cruz (@tedcruz) November 5, 2017

On Monday, Sen. Ted Cruz of Texas avoided questions about gun control in the wake of the attack, saying that the gunman would've killed more people if an armed resident hadn't shot him.

"It is an unfortunate thing that the immediate place the media goes after any tragedy … is politicizing it," Cruz said.

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Staff writers David McSwane, Todd Gillman, Julieta Chiquillo, Terri Langford and The Associated Press contributed to this report.

CORRECTION, 10:20 p.m. Nov. 5, 2017: An earlier version of this story said Devin Kelley received a dishonorable discharge after a court-martial. He received a bad-conduct discharge.