A heavily pregnant mother and three of her children were among 26 people killed by a gunman at a Texas church.

Eight members of the same extended family were reported to have died when Devin Patrick Kelley opened fire on parishioners during Sunday morning service at First Baptist Church in Sutherland Springs. The 14-year-old daughter of the church's pastor was also killed.

Twenty-three of the dead were found inside the building, two were outside, and another died on the way the hospital. Up to 14 children are thought to have been shot.

About 20 others were injured and police have warned the death toll could rise.

The victims ranged in age from five to 72. They included a number of family members and friends from the tight-knit community of about 400 people.

Here is what we know so far about the victims of the worst shooting in the history of modern Texas.

Annabelle Pomeroy

The 14-year-old daughter of the church's pastor, Frank Pomeroy, was the first person identified as killed in the massacre. The clergyman and his wife Sherri were out of town when the shooting happened.

Pastor's daughter Annabelle Pomeroy was killed in the shooting (Facebook)

"We lost our 14-year-old daughter today and many friends," said Ms Pomery in a text message. "Neither of us has made it back into town yet to personally see the devastation. I am at the Charlotte airport trying to get home as soon as I can."

"Heaven truly gained a real beautiful angel this morning along with many more," Annabelle's uncle, Scott Pomeroy, wrote on his Facebook page.

Crystal Holcombe and three children

Mother-of-five Crystal Holcombe died alongside three of her children, according to her cousin Nick Uhlig. He said she was eight months pregnant.

Ms Holcombe's two other children were injured but survived, as did their father John Holcombe, whose parents Bryan and Karla were killed.

Shooting victim Crystal Holcombe pictured with husband John, who survived

Mr Uhlig told the Houston Chronicle his cousin was a devoted mother.

"She doesn't even drink, smoke or nothing," he said. "She just takes care of kids, she raises goats and makes homemade cheese. That kind of thing, you know? They don't go out dancing or anything like that. They're real old-fashioned, down-to-earth."

Bryan, Karla, Marc Daniel and Noah Holcombe

Bryan Holcombe, an associate pastor at the First Baptist Church, was reportedly walking up to the pulpit to lead the congregation in worship when the gunman burst in. He was killed along with his wife Karla and adult son Marc Daniel, his parents told the Washington Post.

Marc Daniel Holcombe's one-year-old son Noah was also said to be among the dead.

Bryan and Karla Holcombe had attended the church for 25 years (&copy; facebook) (© facebook)

“This is unimaginable. My father was a good man, and he loved to preach. He had a good heart,” Scott Holcombe, Bryan’s son, told the New York Times.

Bryan also sometimes worked as a prison minister, according to Mr Uhlig.

"He would go up to the prison with a ukulele to sing," he said.

Joann Ward, Emily Garza and Brooke Ward

Mother-of-four Joann Ward was killed along with daughters Brooke Ward, five, and Emily Garza, seven.

Her son Ryland Ward, five, and his nine-year-old sister Rihanna Garza survived. Ryland was shot four times in the stomach and is reportedly in a stable condition in hospital.

Ms Ward was said to have saved one of her children by using her body as a shield.