Police killed the perpetrator of Monday's shooting in Nashville, Tennessee, identified by authorities as local resident Audrey Elizabeth Hale, when they stormed the Covenant School within minutes of gunfire erupting in the private church-based academy.

Authorities did not immediately offer a motive for the killings. But Nashville Police Chief John Drake said in an NBC News interview that investigators believed Hale harbored "some resentment for having to go to that school" as a child. Drake did not elaborate.

During an earlier press briefing, the chief said Hale self-identified as being transgender, though Drake offered no further clarity. Drake and other officials repeatedly referred to the suspect with female pronouns.

Hale used male pronouns on a LinkedIn page that listed recent jobs in graphic design and grocery delivery.

Among various pieces of evidence under examination by police and FBI agents conducting an investigation were some writings by the assailant, including a "manifesto" and a detailed, hand-drawn map of the school showing various entry points, Drake said.

The chief told NBC the manifesto "indicates there was going to be shootings at multiple locations and that the school was one of them." He said the Covenant School was singled out for attack but that the individual victims were targeted at random.

SHOT THROUGH DOOR TO GAIN ENTRY

Authorities said Drake, armed with two assault-style weapons, one of them a rifle, as well as a 9 millimeter pistol, gained entry to the school by shooting through the window of a side door.

Surveillance camera video posted online by police on Monday night shows the suspect, wearing camouflage pants and a black vest over a white T-shirt, with a red baseball cap on backwards, blasting through the glass pane of an outer door after driving up to the building in a car. The footage then shows the assailant stalking through a hallway as alarm lights flash.

The Metropolitan Nashville Police Department began receiving calls about a shooter at 10:13 a.m., and arriving officers reported hearing gunfire coming from the building's second floor, police spokesperson Don Aaron told reporters.

Two officers from a five-member team shot the assailant in a lobby area, and the suspect was pronounced dead by 10:27 a.m.

"The police department response was swift," Aaron said.

The three slain school children, all age 9, were identified as Evelyn Dieckhaus, Hallie Scruggs, and William Kinney. Also shot dead were staffers Mike Hill, 61, a school custodian, Cynthia Peak, 61, a substitute teacher, and Katherine Koonce, 60, listed on the Covenant website as "head of school."

Reacting to the latest bloodshed in an epidemic of gun violence turning U.S. schools into killing zones, U.S. President Joe Biden urged the U.S. Congress again to pass tougher gun reform legislation, including an assault weapons ban.

"We have to do more to stop gun violence," Biden said at the White House. "It's ripping our communities apart, ripping the soul of this nation."

The Covenant School, founded in 2001, is a ministry of Covenant Presbyterian Church in the Green Hills neighborhood of Nashville with about 200 students, according to the school's website. The school serves preschool through sixth graders and held an active-shooter training program in 2022, local television station WTVF-TV reported.

Monday's violence in Nashville marked the 90th school shooting - defined as any incident in which a gun is discharged on school property - in the U.S. so far this year, according to the K-12 School Shooting Database, a website founded by researcher David Riedman. Last year saw 303 such incidents, the highest of any year in the database, which goes back to 1970.

(Reporting by Sandra Stojanovic in Nashville; Additional reporting by Daniel Trotta, Kanishka Singh, Tyler Clifford, Rich McKay, Brad Brooks, Joseph Ax, Brendan O'Brien and Jonathan Allen; Writing and additional reporting by Steve Gorman; Editing by Stephen Coates)

By Sandra Stojanovic