A 12-year-old boy stabbed six children at a school in Azambuja, Portugal, leaving one seriously injured and the others with minor wounds.

The victims, aged 11 to 14, included five girls and one boy.

The attacker, who is in custody, reportedly returned to the school with a knife and a bulletproof vest after an argument.

The stabbing appeared to be random. Portuguese Prime Minister Luís Montenegro condemned the rare attack, and local authorities are investigating.

Eyewitnesses described the chaotic scene, with children covered in blood, the Mirror has reported.

The suspect’s bulletproof vest is believed to belong to his father.

Written by B.C. Begley