ZAGREB — A seven-year-old girl has been killed and eight others have been injured in a knife attack at an elementary school in the Croatian capital Zagreb.

The 19-year-old attacker, believed to be a former student, entered a first-grade classroom at the Prečko Elementary School early Friday morning and attacked the teacher and several children with a knife, CNN affiliate N1 reported.

Helicopters have been transporting the wounded to hospitals across the city. The teacher sustained life-changing injuries and is in critical condition, the Sveti Duh Hospital said.

“The attacker is under police custody. The injured persons are receiving medical treatment,” Zagreb police said.

Witnesses reported chaotic scenes as ambulances rushed to the school and people fled the building. Videos shared on social media showed dozens of people running away from a building across the school’s sports fields.

Various officials, including the city’s mayor Tomislav Tomasevic and Interior Minister Davor Bozinovic, are on the scene, N1 said.

Prime Minister Andrej Plenkovic said the country is “appalled” by the “tragedy.” He said Health Minister Irena Hristic will visit the hospitals where the wounded are being treated.

School attacks are rare in Croatia and the Balkan region. Last year, Serbia was rocked by two mass shootings in as many days, the first of which targeted a school in the capital Belgrade. — CNN