Are there documentaries on school rampages or plane crashes?

Is there such a thing on Netflix, if so how can I find it there?

Yes, there are documentaries like that and no, they don't exist on Netflix. If there are some on Netflix or should still be, you can find them under the category documentation or just "documentation". There are also sub-categories in each case.

I think it's more likely to be found on YouTube…

Yes, but you already know them all

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There are plenty of them, just hard to get hold of.