A 15-year-old kills a caretaker at a school in Leszczydol-Nowiny

A 15-year-old former pupil killed a 37-year-old caretaker and injured two other staff on Thursday morning at a primary school in Leszczydol-Nowiny, in Wyszkow County, northeast of Warsaw. Police said resuscitation failed. The headteacher, who stopped the boy, and a teacher were wounded. Interior ministry spokesperson Karolina Galecka said their lives are not in danger. The boy entered the school at about 9:00 am local time, 7:00 GMT. Galecka said he was carrying three knives. His motive is not known. Polish media said the caretaker had tried to stop him at the door.

Thursday's killing is the second school attack in Poland in two days, and police say they broke up a third plan in between. On Wednesday a 19-year-old was arrested after a stabbing at a school in Ostroleka, in the northeast. Reuters put the wounded there at 10, including the suspect. An earlier wire count said seven were hurt, and a day-page entry said nine. The suspect was himself injured and was detained soon after. On a separate tip, police in Sierpc, north-west of Warsaw, detained a 17-year-old who had said on school grounds that he planned to do something dangerous and to harm someone. Interior minister Marcin Kierwinski said officers found two knives in his backpack. Mazowsze police had announced that arrest before the Leszczydol-Nowiny attack was public.

The three cases are not one plot. They are three boys, in three towns, in two days, with blades rather than firearms. Poland's interior ministry has treated them as a cluster all the same. Galecka's detail that the Leszczydol-Nowiny suspect is a former pupil, not a current one, narrows the security question. A gate check aimed at enrolled students would not have caught him on a roll. The caretaker met him at the entrance. The headteacher then held him until police arrived, which the force said was within minutes of the call. That sequence is the whole of the known intervention. There is no report of a shot fired by police.

The age of the suspects will shape the process. A 15-year-old and a 17-year-old fall under juvenile rules. A 19-year-old can be charged as an adult. The ministry has not said what charge the 15-year-old will face, only that he is in custody and that the caretaker died despite resuscitation. Naming the dead man will wait on the family. Police have given the age, 37, and the job. They have not given a name in the statements used by Reuters and the BBC.

For other schools the immediate change is local, not a new statute. Wyszkow County and the neighbouring districts now have a dead staff member, a wounded headteacher, and a minister who has already described a prevented attack in Sierpc. Kierwinski's public line on the 17-year-old was that the boy had said, on school grounds, that he intended to harm someone. That is a speech case as well as a weapons case. The knives in the backpack are what the search found after the words. Schools that ask what to do with a similar remark have Thursday's example: Sierpc was stopped, Leszczydol-Nowiny was not.

The numbers to keep straight, because the wires do not agree on Ostroleka, are these. Leszczydol-Nowiny: one dead, two injured, suspect aged 15, former pupil, about 9:00 am, three knives, headteacher among the injured and among those who stopped him. Ostroleka, Wednesday: suspect aged 19, himself hurt, wounded put at seven, nine or 10 depending on the desk and the hour. Sierpc: suspect aged 17, two knives, no attack carried out. Any later official toll should replace the Ostroleka range, not be added to it.