The violence occurred at The Covenant School, a Presbyterian school for about 200 students from preschool through sixth grade.
Police said the shooter appeared to be in her teens and was armed with two assault-type rifles and a pistol.
The Nashville victims were pronounced dead upon arrival at the Monroe Carell Jr Children’s Hospital, according to Craig Boerner, a spokesperson for Vanderbilt University Medical Center, which is affiliated with the children’s hospital.
Other students walked to safety on Monday, holding hands as they left their school surrounded by police cars, to a nearby church to be reunited with their parents.
Police officers with rifles, heavy vests and helmets could be seen walking through the school parking lot and around the grassy perimeter of the building Monday morning.
Helicopter footage from WTVF also showed the officers looking around a wooded area between the campus and a nearby road.
Jozen Reodica heard the police sirens and fire trucks blaring from outside her office building nearby. As her building was placed under lockdown, she took out her phone and recorded the chaos.
“I thought I would just see this on TV,” she said.
“And right now, it’s real.”
On WTVF TV, reporter Hannah McDonald said her mother-in-law works at the front desk at The Covenant School.
The woman had stepped outside for a break Monday morning and was coming back when she heard gunshots, McDonald said during a live broadcast.
The reporter said she had not been able to speak with her mother-in-law but her husband had.
The Covenant School was founded as a ministry of Covenant Presbyterian Church in 2001, according to the school’s website.
The school is located in the affluent Green Hill neighbourhood just south of downtown Nashville, situated close to the cities top universities and home to the famed Bluebird Cafe – a beloved spot for musicians and song writers.
The grade school has 33 teachers, the website said. The school’s website features the motto “Shepherding Hearts, Empowering Minds, Celebrating Childhood”.
Democratic state Representative Bob Freeman, whose district includes The Covenant School, called Monday’s shooting an “unimaginable tragedy”.
“I live around the corner from Covenant and pass by it often. I have friends who attend both church and school there,” Freeman said in a statement.
“I have also visited the church in the past. It tears my heart apart to see this.”