A 14-year-old boy has died and five other people have been injured in a knife attack in southern Austria on Saturday, according to police, who said they had arrested a 23-year-old suspect.

The suspect was detained in the city of Villach, where the attack took place, police said on Saturday. He is a Syrian national with legal residence in Austria, they said.

The victims were all men. Two were seriously injured, according to police.

A police spokesperson, Rainer Dionisio, said a motive was not immediately known. He added that police were investigating the attacker’s personal background. “We have to wait until we get secure information,” he said.

A 42-year-old man who works for a food delivery company, and who is also from Syria, witnessed the incident from his car, police said. He drove toward the suspect and helped to prevent things from getting worse, Dionisio told Austria’s public broadcaster, ORF.

Peter Kaiser, the governor of the Austrian province of Carinthia, expressed his condolences to the family of the 14-year-old victim.

“This outrageous atrocity must be met with harsh consequences. I have always said with clarity and unambiguously: those who live in Carinthia, in Austria, have to respect the law and adjust to our rules and values.”

Erwin Angerer, a lawmaker for the far-right Freedom party, said his party had been warning about the situation in Austria as a result of the country’s “disastrous asylum policy”.

Austria’s interior minister, Gerhard Karner, was expected in Villach on Sunday morning.

Police said it wasn’t clear whether the suspect acted on his own and continued to search for potential additional suspects.

Several European countries, among them Austria, said in December they are suspending decisions on asylum claims by Syrian nationals because of the unclear political situation in their homeland following the fall of Bashar al-Assad.

Agence France-Presse contributed to this report