At least 27 people have been reported dead after a gunman opened fire at the First Baptist Church in Sutherland Springs in Wilson County.
The gunman, currently unidentified, is said to have been killed in the police response.
Police official Albert Gamez Jr confirmed the number of fatalities to CBS News.
“The details are kind of sketchy but what I know right now, what they’re telling me, like 27 deceased and over 20, 25 injured,” Mr Gamez Jr said. “They’re talking about the shooter is dead also,” he added.
The shooter walked into the church shortly before noon – at a morning service that witnesses said was normally attended by some 50 people and opened fire. A two-year-old was among the wounded, the Dallas Morning News website reported.
The gunman died after a brief car chase into nearby Guadalupe County slightly to the north, a Sherriff’s Office deputy from that county told CNN.
The San Antonio FBI branch said its agents had been deployed, and there was no indication of the gunman’s motive.
The FBI also said that while only one shooter was reported, it was looking into other possibilities.
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.”
President Trump, on a tour of Asia, tweeted: “May God be with the people of Sutherland Springs, Texas. The FBI and law enforcement are on the scene. I am monitoring the situation from Japan.”
The shooting comes just over a month after a gunman in Las Vegas, firing down from a hotel room, killed 58 people and wounded hundreds attending an outdoor concert.
And it came just over two years after a white supremacist, Dylann Roof, entered a historically black church in Charleston, South Carolina, and shot nine people to death.