Orlando Harris, the now-deceased suspect in Monday's St. Louis school shooting, used an AR-15-style rifle and brought more than 600 rounds of ammunition to the attack, police announced Tuesday.

Authorities also recovered a notebook in which Harris, 19, had written about his desire to carry out a school shooting. His attack on the Central Visual and Performing Arts High School killed two victims — a female student and her teacher — and injured seven others.

"The suspect, in addition to the rifle, brought in a large quantity of ammunition," St. Louis Police Chief Michael Sack said in a Tuesday press conference. "He had seven magazines of ammunition on a chest rig he wore. He also had an additional eight magazines of ammunition in a field bag he carried."

Harris also placed further magazines full of ammunition in hallways and stairways just prior to his attack.

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Students evacuate the Central Visual and Performing Arts High School in St. Louis on Monday, Oct. 24, 2022. (KTVI) (KTVI)

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Sack added that FBI investigators had uncovered a handwritten document inside Harris' vehicle in the school parking lot.

"He [wrote] about his desire to engage in this incident. To conduct a school shooting," Sack said before reading a portion of the notebook.

"He wrote, quote, ‘I don’t have any friends. I don't have any family. I've never had a girlfriend. I've never had a social life. I've been an isolated loner my entire life. This was the perfect storm for a mass shooter,' end quote," Sack said.

The police chief said there were no updates regarding the injured victims who remain in the hospital.

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Law enforcement personnel investigate the scene of a shooting at Central Visual and Performing Arts High School, Oct. 24, 2022, in St. Louis. (AP Photo/Jeff Roberson)

Officers received a call around 9:10 a.m. about an active shooter at the school on Monday morning. Within minutes, authorities arrived and entered the school as students were fleeing the building, Sack said during Monday's press conference.

"Upon hearing gunfire, they ran to that gunfire, located the shooter and engaged that shooter in an exchange of gunfire," the chief told reporters.

Sen. Josh Hawley, R-Mo., praised the "swift response of local law enforcement" in a statement to Fox News.

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"Devastating news in St. Louis," he wrote. "My office is in contact with local authorities, and we stand ready to offer all assistance possible."