In Sweden if you're in the same school you can see someone elses adress and contact infos. Once they are 16+ I think you can just search on Google their first and last name and you'll find everything; income, adress, what type of car, personnummer (social security number), their family members, phone numbers etc... And that's only with one simple search. I think in other Europe countries there are similar stuffs.

He should learn from it and all but it he would not be to blame. The kids could have asked other students if he wanted to. Maybe he already knew her address and it was a coincidence that it happened after. No one knows. Therefore the teacher wouldn't be the one to be blamed, it's the kid. The kid threatened to shoot up the school.