Six people - including three children - are dead after a transgender female shooter opened fire at a private school in Nashville, killing three nine-year-old children and three staff members. 

The shooter was 28-year-old Audrey Hale, who at one time attended the school. 

Police said she identified as transgender, and online profiles show Audrey used 'he/him' pronouns.

At around 10.13am, she opened fire at The Covenant School, shooting and killing nine-year-old Evelyn Dieckhaus, Hallie Scruggs and William Kinney. 

Scruggs was the daughter of Chad Scruggs, the pastor at the affiliated presbyterian church. 

Substitute teacher Cynthia Peak, 61, head of school Katherine Koonce, 60, and custodian Mike Hill, 61, were also killed.

It's unclear what Hale's motive was, but police believe she attended the school at some point. She had detailed, drawn maps of the school and had been surveilling it, according to police. 

'We have a manifesto, we have some writings. We have a map drawn out of how this was all going to take place,' Nashville Police John Chief Drake said. 

The small school is run by a church and does not employ a school resource officer.