The suspect shot himself during a struggle with an usher from the church in Antioch, but survived his wound.
The usher, who was struck in the face by the gun, fetched his own gun from his car and guarded the gunman until police arrived.
Police said the usher acted in an "extraordinarily brave" way.
One woman, named as 39-year-old Melanie Smith of Smyrna, was found dead in the car park near the suspect's car.
Nashville Police said the suspected attacker at the Burnette Chapel Church of Christ was Emanuel Kidega Samson, 25, who was originally from Sudan.
They added that the gunman shot himself in the chest "probably not intentionally" during the struggle with the usher, and that he has since been released from hospital.
He will be charged with murder and attempted murder.
"It would appear he was not expecting a brave individual like the church usher to initiate the struggle and confrontation," Nashville Police spokesman Don Aaron said.
"This gentleman, this church usher (is) an extraordinarily brave individual."
The motive for the shooting is not yet clear.
At least six people were wounded, all of whom were aged over 60, with the exception of the young usher.
The church's pastor, Joey Spann, and his wife Peggy were among those injured in the shooting, the Nashville Christian School said. Mr Spann teaches at the school.
One eyewitness, speaking to the Tennessean newspaper, said the pastor had shouted "run" as the suspect entered, but some were shot from behind.
"Our church is senior people. They didn't make it out," Minerva Rosa told the paper.