Sherri Pomeroy, wife of Pastor Frank Pomeroy, said she lost her daughter "and many friends" in the shooting.

She said both she and her husband were out of town and trying to get back to Sutherland Springs, outside of San Antonio.

Frank Pomeroy told ABC News by phone that Annabelle "was one very beautiful, special child".

A witness reported seeing a man dressed in combat gear walk into the First Baptist Church and begin shooting around 11.30am local time.

Local media said at least 15 people - including a 2-year-old - were injured.

Neighbours near the church said they heard the shooter reload "multiple" times while a service was being held. They say about 50 people usually attend services there.

At least six helicopters were called to the scene to take the injured to hospital

A tight-knit community

Carrie Matula, who works at a gas station near the church, told MSNBC that she heard "semiautomatic gunfire" and looked to see what was going on.

"I never thought it would happen here," Matula said. "This is something that happens in a big city. I would never have thought this would have taken place here. It's just too tight a community. It doesn't make sense."

A woman who lives about 10 minutes away from Sutherland Springs in Floresville and was monitoring the chaos on a police scanner and in Facebook community groups, said that everyone knows everyone in the sparsely populated county.

"This is horrific for our tiny little tight-knit town," said Alena Berlanga.

"Everybody's going to be affected and everybody knows someone who's affected," she said.

The population of Sutherland Springs is said to be only about 400 people.

Texas Governor Greg Abbott said: "Our prayers are with all who were harmed by this evil act.

"Our thanks to law enforcement for their response."

The mass shooting comes just a month and five days after Stephen Paddock killed 58 people by opening fire on a concert in Las Vegas from his hotel room.