ST LOUIS, United States (AP) — A gunman broke into a St Louis high school Monday morning, fatally shooting a woman and a teenage girl and injuring six others before police killed him in an exchange of gunfire.

The shooting, just after 9:00 am 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 terrorised 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, Police Commissioner Michael Sack said the shooter was about 20 years old but did not provide a name for him or his victims. He declined to say if the woman killed was a teacher.

St Louis Schools Superintendent Kelvin Adams said seven security guards were in the school at the time, each at an entry point of the locked building. One of the guards noticed the man was trying to get in at a locked door but couldn’t. The guard notified school officials and ensured that police were contacted, Sack said.

“It was that timely response by that security officer, the fact that the door did cause pause for the suspect that bought us some time,” Sack said.

Sack declined to say how the man eventually got inside, armed with what he described as a long gun.

Officers worked to get students out of the three-storey brick building, then “ran to that gunfire, located that shooter, and engaged that shooter in an exchange of gunfire”, killing him, Sack said.

Some of the six people hospitalised suffered gunshot wounds, while others were struck by shrapnel, Sack said. He did not provide any information on their conditions.

One student, 16-year-old Taniya Gholston, told the St Louis Post-Dispatch she was in a room when the shooter entered.

“All I heard was two shots and he came in there with a gun,” Gholston said. “And I was trying to run and I couldn’t run. Me and him made eye contact but I made it out because his gun got jammed. But we saw blood on the floor.”

Ninth-grader Nylah Jones told the St Louis Post-Dispatch she was in maths class when the shooter fired into the room from the hallway. The shooter was unable to get into the room and banged on the door as students piled into a corner, she said.

Janay Douglas’s 15-year-old daughter got stuck in a hallway when the school was locked down. Douglas said she received a call from her daughter letting her know she had heard shots.

“One of her friends busted through the door, he was shot in the hand and then her and her friends just took off running. The phone disconnected,” Douglas said. “I was on my way.”

The shooting left St Louis Mayor Tishaura Jones shaken.

“Our children shouldn’t have to experience this,” Jones said at the news conference. “They shouldn’t have to go through active shooter drills in case something happens. And, unfortunately, that happened today.”

Central Visual and Performing Arts High School is a magnet school, specialising in visual arts, musical art, and performing arts, with about 400 students. The district website says the school’s “educational programme is designed to create a nurturing environment where students receive a quality academic and artistic education that prepares them to compete successfully at the post-secondary level or perform competently in the world of work”.