At least 12 to 14 children are among the victims in the tragic Texas church shooting, the local sheriff has said as details of families losing loved ones continue to come out.

As least 26 were left dead and 20 injured following the mass shooting at the First Baptist Church in Sutherland Springs.

Police have now said the range of those died in the church is from 18 months to 77 years old, having previously stated that those being treated in the hospital ranged from age five to 72.

Sheriff Joe Tackitt said “seeing the children, that’s what hurts the most” regarding the scene inside the small Baptist church.

It has been confirmed that one of the children who died was 14-year-old Annabelle Pomeroy, the daughter of the First Baptist Church's Pastor Frank Pomeroy and wife Sherry.

The Pomeroys were actually out of town during the Sunday service which their daughter had attended.

Her father said Annabelle “was one very beautiful, special child" and Ms Pomeroy issued a statement in which she the congregation was more like a family than just those attending the same church.

Bryan Holcombe, the associate pastor, was walking up to the podium to continue the service when the shooting began. He and wife Karla are among those killed.

Another adult victim was their daughter-in-law Crystal Holcombe, a mother of two daughters who was also eight months pregnant according to relatives who spoke to the Associated Press.

Joanne Ward and her three children, aged between five and eight according to a family friend who spoke to the LA Times, were among those wounded by suspected gunman Devin Kelley, 26, of nearby Comal County, Texas.

CNN has reported that at least eight of the victims were from the same family, including at least three children.

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Mr Kelley, clad in a black tactical vest and reportedly brandishing an AR-15-style assault rifle, allegedly shot at least one person outside of the small building in a rural suburb of San Antonio.

He then strode into the open-door service and began shooting.

Once done, he tried to flee the scene but an unidentified neighbour armed with a gun opened fire on him outside. It forced Mr Kelley to drop his weapon and attempt to escape in his SUV.

"It's really loud. At first I thought someone was blasting," said Ryan Albers, 16, who lives across the road. "It had to be coming from somewhere pretty close. It was definitely not just a shotgun or someone hunting. It was someone using automatic weapon fire."

Johnnie Langendorff, another one of Sutherland Spring's 600 residents, happen to be driving by in his truck when he came upon the scene.

"I pulled up to the intersection where the shooting happened. I saw two men exchanging gunfire, the other being the citizen of the community. The shooter of the church had taken off, fled in his vehicle, the other gentleman came and said we need to pursue him. And that’s what I did, I just acted," Mr Langendorff told local television station KSAT.

Police have spoken with the man who confronted Mr Kelley with gunfire and Mr Tackitt said "he doesn’t believe he’s a hero, but I believe he is.”

Mr Kelley reportedly lost control of the car about "twelve to fifteen minutes" into the chase according to what Mr Langendorff told CNN.

Police have confirmed the suspected shooter's death, and Mr Tackitt told CBS News that it was the result of a self-inflicted gunshot wound.

A motive has not been identified as yet, but it has been confirmed that Mr Kelley's in-laws, and possibly his estranged wife, were members of the congregation. None were attending service the day of the shooting.

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Mr Kelley does not appear to have attended services there and police have said they do not believe the incident was religiously or racially motivated, but rather a domestic matter.

He was in the US Air Force between 2010 and 2014 at the Logistics Readiness at Holloman Air Force Base in New Mexico, but was given a "bad conduct discharge" which can prevent a person from obtaining a license to own a firearm.

Authorities are still investigating exactly how Mr Kelley was able to purchase firearms.

US Air Force Spokeswoman Ann Stefanek said Mr Kelley served 12 months' confinement after a 2012 court-martial after abusing his wife and child, resulting in a reduction in rank and eventual discharge.

Police vehicles were spotted outside of Mr Kelley's listed address in New Braunfels, Texas residence, about 35 miles (56 km) away from Sutherland Springs.

At least some of the victims had to flown from the scene to a trauma centre hospital in San Antonio, others were taken to a local hospital.

Ten remain in critical condition and six in serious condition according to Freeman Martin of the Texas Department of Public Safety but hospital officials have not released details on the specific injuries or identities.

Four are in stable condition and some have been released.

Fred Milanowski, Special Agent in Charge from the Alcohol, Tobacco, and Firearms law enforcement agency (ATF), said three weapons - one rifle and two handguns - were recovered from the scene and identified as items purchased by Mr Kelley.

There is reportedly video from inside the church of the service but police have not released details on the tape as yet.