Gunman is dead: reports
With details rapidly unfolding, some unnamed officials were quoted as citing tolls as high as 27 dead and 20 or more wounded.
The shooter was also dead, Guadalupe County Sheriff's spokesman Sergeant Robert Murphy told AFP, without providing further details about the circumstances of his death.
The worshippers were gunned down at First Baptist Church in Sutherland Springs, a small rural community about 30 miles (50 kilometers) southeast of San Antonio, reports said.
Wilson County Commissioner Albert Gamez Jr told AFP there were multiple fatalities and multiple people wounded, but he could not officially confirm the number.
The shooter reportedly 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 reported.
It was unclear how the shooter died.
"There was no police chase," Murphy said, denying earlier media reports that the gunman was killed after a pursuit. "He was in his vehicle."
A spokeswoman for Connally Memorial Medical Center in nearby Floresville said the hospital received eight patients with gunshot wounds. Four had been transferred to San Antonio.
- Federal agents assisting -
A witness working at a gas station across the street told CNN he heard at least 20 shots being fired in quick succession. Others nearby said the shooter appeared to have reloaded more than once.
Emergency personnel rushed to the scene in the community of 400 people, and some victims were evacuated by helicopter.
Police formed a perimeter around the area. Tearful relatives and neighbors stood outside, nervously awaiting news from inside the traditional, white-frame church.
Agents from the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives were heading to Sutherland Springs, the agencies said.
President Donald Trump, who is in Japan on the first stop of a tour of Asian countries, tweeted: "May God be w/ the people of Sutherland Springs, Texas. The FBI & law enforcement are on the scene. I am monitoring the situation from Japan."
Texas Governor Greg Abbott offered his condolences.
"Our prayers are with all who were harmed by this evil act. Our thanks to law enforcement for their response," he said, promising more details "soon."
The shooting comes just over a month after a gunman in Las Vegas fired down from a hotel room onto an outdoor concert, killing 58 people and wounding hundreds.
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.
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