A pastor of a neighboring church told local TV media that he knows numerous victims, and he is confident that the victims are "in the loving arms of Jesus" right now.
Sutherland Springs is a community of about 400 people 30 miles (48 kilometers) southeast of San Antonio.
A witness told local news channel KENS5 that a child was among those who was shot.
Police have confirmed the man who opened fire is now dead following a short pursuit and said there were "multiple victims".
President Donald Trump said he was monitoring the situation while in Japan on a 12-day Asian trip.
2 dead, 1 injured in shooting at Colorado Walmart, police say
Thornton police say 47-year-old Scott Ostrem was arrested Thursday morning, about 14 hours after he fled the store in a vehicle . Almost 50 witnesses were reportedly taken to a nearby police station in the wake of the shooting before being released.
Emergency officials are on scene and updated reports are expected.
It was unclear if the shooter was killed by police or took his own life, Mr Murphy said.
Agents of the Federal Bureau of Investigation, the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives and other law enforcement agencies were either on the scene or traveling there.
After the shooting, the suspect sped away in a auto and was soon cornered by sheriff's deputies just outside of Wilson County in Guadalupe County, Wiley told Reuters.
The church is a white, wood-framed building with a double-door at the entrance and a Texas flag on a pole at the front area, according to its website, which was down shortly after the shooting.
"It was rapid fire", Matula said.