The Nashville school shooter had a ‘manifesto’ and maps, police say.

The attacker who fatally shot three children and three staff members at a Nashville school on Monday was identified as a former student at the school who the police said appeared to have written a manifesto about the attack and drawn maps of the campus.

The shooter, identified as Audrey E. Hale, was killed by police officers who responded to the shooting at the Covenant School, a small, private Christian school that is attached to a church and serves children from pre-school through sixth grade.

The Nashville police chief, John Drake, said the police had found maps of the school that were drawn “in detail” and which noted the location of school surveillance cameras, entry points and other features. He said the police were in touch with the shooter’s father, and that it was not immediately clear when the assailant had attended the school.

The attacker entered the school by shooting through one of the doors, the authorities said, and was armed with three guns, including an AR-style rifle, an AR-style pistol and a handgun. At least two were purchased legally in the Nashville area, the police said.

The assailant was “prepared for a confrontation with law enforcement” and “prepared to do more harm” before being killed, Mr. Drake said.

There was confusion about the gender identity of the assailant in the immediate aftermath of the attack. Officials used “she” and “her” to refer to the shooter, and Chief Drake said that the assailant identified as transgender.

Kristin Mumford, a police spokeswoman, said that the shooter had been born female but listed male pronouns on a LinkedIn profile, which suggested that the suspect was a transgender man. That profile had been active in recent months, with the user reacting to two posts about other people’s career updates.

In response to a reporter’s question about whether the attacker’s gender identity was connected to the shooting, Chief Drake said, “We’re investigating all the leads.”

The attacker was an illustrator and graphic designer who had studied at the Nossi College of Art and Design, according to a former teacher and an online portfolio.

“She just always was a kind of quiet girl but was very serious about her work,” said Steve LaSuer, an instructor at the school who had taught the attacker in a design and composition in 2015 or 2016. Mr. LaSuer said he had been stunned by Monday’s developments. “It’s blown me away,” he said.

The online portfolio included illustrations related to businesses around Nashville, including logos and splashy advertisements for a restaurant, a toy store and a video company. Beginning last May, the shooter worked as a shopper for a grocery delivery company, according to a LinkedIn profile.

Kitty Bennett and Kirsten Noyes contributed research.