ST. LOUIS (KTVI) – The 19-year-old gunman who killed two people at a St. Louis school Monday was armed with 600 rounds of ammunition, police said at a press conference Tuesday.

Orlando Harris opened fire at Central Visual and Performing Arts High School Monday morning. In addition to the two people killed, seven were injured.

Police later shot and killed Harris.

“The threat here is over. However, we’re going to continue to be vigilant in our schools and in our neighborhoods, to be present and alert for situations that could create harm in our community,” said Michael Sack, interim St. Louis Police Chief, during the news conference Tuesday.

Sack confirmed Harris entered the building with only one weapon, an AR-15 rifle, but with more than 600 rounds of ammunition. That included seven magazines of ammunition on a chest rig he wore and eight magazines of ammunition in a field bag he carried.

Sack confirmed Tuesday that Harris entered the building with only one weapon, an AR-15 rifle, but with more than 600 rounds of ammunition. (Photo courtesy: KTVI via St. Louis Metropolitan Police Department)

DeAndre Davis, Director of Safety and Security for St. Louis Public Schools, said Harris did not enter the school through a checkpoint. Within minutes of being notified, police responded to the scene and exchanged gunfire with Harris.

Davis said the security officers at the high school were not armed.

According to Sack and Davis, officers with the St. Louis Metropolitan Police Department were trained in active-shooter situations about a month ago, including officers who assist with St. Louis Public Schools.

“Officers were aware of what happened, the magnitude of what was happening,” said Davis. “Our officers were there and directing responding officers directly where the shooter was. … They did exactly what they were supposed to do.”

Harris was a graduate of the high school and had no prior criminal history. While the exact motive has not yet been determined, police presented some documents Tuesday that may provide some clues.

Paperwork inside a car tied to Harris included this handwritten note:

“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.”

Handwritten note in St. Louis school shooting suspect’s car

“We can see some of what’s going on inside his mind,” said Sack. “He feels isolated, he feels alone, quite possibly angry and resentful of others. … So a desire to lash out.”

The two people killed were identified as tenth-grader Alexandria Bell and 61-year-old physical education teacher Jean Kuczka.

The seven injured students are all 15 or 16 years old. All were listed in stable condition. Sack said four suffered gunshot or graze wounds, two had bruises and one had a broken ankle — apparently from jumping out of the three-story building.

Sack reminded community members of the “see something, say something” approach to address any suspicious behavior, particularly any comments involving guns with people dealing with mental health struggles.

Police officers and FBI agents stand outside the north side of the Central Visual and Performing Arts High School after a shooting that left three people dead including the shooter in St Louis, Missouri on October 24, 2022. – (Photo by Tim Vizer/AFP via Getty Images)

St. Louis Mayor Tishaura Jones said the tragedy is one of many that should heighten action over gun control.

“The scourge of gun violence that continues to claim our children and families in their communities is a national emergency,” said Jones. “It’s a public health crisis that requires federal action.”

Meanwhile, the St. Louis Public Schools district has activated three new resources for mental health since Monday. The district said it is also working on a long-term plan.

“We’re collaborating with our community partners, as well as the mayor’s office and U.S. Department of Education,” said Dr. Michael Brown, deputy superintendent of student support services for SLPS.

In light of the shooting, Jones and other speakers Tuesday encouraged people to call the Behavioral Health Response’s 24/7 hotline at 314-469-6644 or text “Be Heard” to 31658 if in need of any additional mental health resources in the St. Louis region.

The Associated Press contributed to this report.