WARSAW, Poland — Police on Saturday said they detained 76 people across Poland and checked nearly 50,000 schools nationwide as part of efforts to prevent further violence following two school attacks earlier in the week.

On Friday, schools across Poland stepped up security, with some suspending classes, many parents keeping children at home and police patrols deployed to educational institutions after two attacks at schools earlier in the week left one person dead and several others wounded, including children.

On Wednesday, a 19-year-old student at a vocational school in the Mazovian province in central Poland attacked fellow students, teachers and passersby with a sharp object, injuring nine people before fleeing and being arrested nearby. The following day, a 15-year-old killed a school custodian and wounded two others in a knife attack at his former school in the same province.

The assaults, both carried out by Polish nationals, shocked a country where school violence by minors is a new phenomenon.

By Thursday night, rumours that the attacks were coordinated and that there would be more on the culmination day dubbed “bloody Friday” were being shared in parents’ online groups and by mainstream media.

59 schools preemptively suspended classes on Friday across Poland, the majority in the Mazovian district, where the capital Warsaw is located. School directors sent messages announcing stepped-up security measures including extra school staff placed at entrances and voluntary backpack checks.

“There will ⁠be no compromise here. The safety of the youth is the most important thing,” Interior Minister Marcin Kierwiński said.

Those detained on Friday include a 14-year-old boy from a central district of Warsaw who was found in possession of a knife with a concealed blade and 11 firecrackers, and a 16-year old from another Warsaw district who came to school with a butterfly knife in his backpack. Others had posted online photos of knives, threatened their peers or threatened school attacks.

So far, the government said, it had found no evidence that an internet challenge promoting school attacks was ongoing. There is also no official confirmation that the two attacks were linked; both perpetrators are in custody.

Parents across Poland are now having to catch up fast on how to speak to their kids about school violence. Authorities say extra security measures at schools will continue and crisis training will be organized. The liberal government also promised to renew efforts to pass a bill blocking harmful online content.

“If that juvenile attacker had streamed the crime online today, we would have been unable to block that content because we have not been given that legal tool,” Prime Minister Donald Tusk said.

After wounding three adults in Thursday’s attack, the 15-year-old, who wore a camera to record his actions, was eventually overpowered by school director Krzysztof Ochmański. Ochmański later told reporters there was a moment when the boy seemed to realise the enormity of his actions and said he did not want to do this any more.

“Once I had established contact, he asked me for help,” Ochmański recounted. “It got to the point where he wanted a hug.”