The shooting happened at the Fire Baptist Church of Sutherland Springs, where an average of 50 people usually attend the morning service, according to local authorities.
Wilson County Commissioner Albert Gamez Jr told CNN that at least 27 people have been killed in the shooting, but the death toll is expected to climb.
'My heart is broken,' Gamez said. 'We never think where it can happen, and it does happen. It doesn't matter where you're at. In a small community, real quiet and everything, and look at this, what can happen.'
Fire Baptist Church Pastor Frank Pomeroy told ABC that his 14-year-old daughter is among the dead. She was 'one very beautiful, special child,' the pastor told.
The shooter was shot down by police after he attempted to flee the scene.
Texas Attorney General Ken Paxton said in a statement: 'The thoughts and prayers of all Texans are with the people of Sutherland Springs as tragic reports come out of First Baptist Church.'
'Please join Angela and me as we pray for those impacted by this horrific shooting,' Paxton said.
The total number of victims is still undetermined as police and local authorities continue their investigation.