NASHVILLE, Tenn. – The shooter who killed six people, including three children, at a Nashville elementary school Monday had detailed maps of the facility, considered another target and left behind writings that may shed light on a motive, authorities said.

The attacker, identified as Audrey Elizabeth Hale, 28, was a former student at The Covenant School who broke in Monday morning by shooting the glass from a door. The intruder gunned down three young students and three staff members before being confronted and killed by police, Metro Nashville Police Department Chief John Drake said.

In surveillance footage released by Nashville police late Monday, Hale is seen driving to the school to carry out the shooting. 

Armed with two AR-style weapons – one a rifle, the other a pistol – along with a handgun, Hale is seen shooting into glass doors to enter the building. The video then shows Hale walking in hallways and aiming an assault rifle before the video cuts off.

According to a tweet from Nashville police, the shooter had “significant ammunition.”Drake said two of the weapons were legally purchased in the Nashville area but did not specify which ones.