The heavily armed female shooter was killed during a shootout with a five-member police team that engaged her on the second floor of the Covenant School, a Presbyterian school associated with a church, authorities said.
She entered the school through a side entrance, and made her way from the first floor of the shoot to the second "firing multiple shots," Nashville Police Department spokesperson Don Aaron said during a news briefing.
She had at least two assault rifles and a handgun on her when she opened fire at the Covenant School. Police are currently attempting to identify the gunwoman, but Metro Nashville Police Chief John Drake said she was a 28-year-old former student at the school. Police have identified where she lives, said Drake.
One officer sustained an injury from a piece of broken glass, but no other injuries were reported.
The victims have yet to be identified, but five of the six were transported to a local hospital before they died. In all, 108 students and staff members were transported away from the scene following the shooting, according to the Nashville Fire Department.
US President Joe Biden decried the shooting, saying it is "sick".
"We're still gathering the facts of what happened, and why. And we do know that as of now there are a number of people who did not make it, including children," said Biden.
"It is heartbreaking, a family's worst nightmare," he said at the White House. "We're monitoring the situation really closely. We have to do more to stop gun violence. It's ripping our communities apart."