ST. LOUIS (AP) - An armed former student broke into a St. Louis high school Monday morning warning, “You are all going to die!” before fatally shooting a teacher and a teenage girl, and wounding seven others before police killed him in an exchange of gunfire.

The attack just after 9 a.m. at Central Visual and Performing Arts High School forced students to barricade doors and huddle in classroom corners, jump from windows and run out of the building to seek safety. One terrorized girl said she was eye-to-eye with the shooter before his gun apparently jammed and she was able to run out.

Speaking at a news conference Monday afternoon, Police Chief Michael Sack identified the shooter as 19-year-old Orlando Harris, who graduated from the school last year.

Sack said the motive is still under investigation but “there’s suspicions that there may be some mental illness that he’s experiencing.” Investigators later searched Harris’ home, Sack said.

Authorities didn’t name the victims, but the St. Louis Post-Dispatch identified the dead teacher as Jean Kuczka. Her daughter said her mother was killed when the gunman burst into her classroom and she moved between him and her students.

“My mom loved kids,” Abbey Kuczka told the newspaper. “She loved her students. I know her students looked at her like she was their mom.”

Sack said the other fatality was a 16-year-old girl who died at the school. He did not release her name.

Seven other 15- and 16-year-old students, four boys and three girls, were all in stable condition. Four students suffered gunshot wounds or graze wounds, two suffered bruises and one had a broken ankle.

Sack declined to say how Harris was able to get into the building, which has security guards, locked doors and mental detectors.

“If there’s somebody who has a will, they’re going to figure out, we don’t want to make it easy for them,” Sack said. “We just got to do the best we can to extend that time it takes them to get into the building to buy us time to respond.”

Harris had the gun out when he arrived at the school and “there was no mystery about what was going to happen. He had it out and entered in an aggressive, violent manner.”

Harris had nearly a dozen high-capacity magazines of ammunition with him, Sack said. “That’s a whole lot of victims ... It’s certainly tragic for the families and it’s tragic for our community but it could have been a whole lot worse.”

St. Louis Schools Superintendent Kelvin Adams said seven security guards were in the school at the time of the attack, each stationed at an entrance of the locked building. One of the guards noticed the gunman trying unsuccessfully to get in at a locked door. The guard notified school officials, who contacted police.