A 7-year-old girl was stabbed to death Friday at an elementary school in Croatia by a knife-wielding teenager who also wounded three other children and a teacher, officials said.

Video footage Friday showed children running away from the school as a medical helicopter was landing.

The attacker is a former student of the Precko Elementary School in Zagreb where the attack took place, according to Interior Minister Davor Bozinovic.

The teen had a history of mental health issues and after Friday's incident "shut himself in a nearby health center where he tried to injure himself with the knife," according to Bozinovic. Police were able to prevent him from committing suicide.

Last year, the teen also tried to kill himself, the minister said.

"Five persons have been hospitalized, and their lives are not in danger," Croatian Health Minister Irena Hrstic said, including the attacker in the count.

"There are no words to describe the grief over the horrible and unthinkable tragedy that shocked us all today," said President Zoran Milanovic.

"We are horrified," said Prime Minister Andrej Plenkovic.

Following the assault at the school, Croatian officials declared Saturday as a day of mourning.