Facts like this are why landmines are almost universally considered to be a crime against humanity though unsurprisingly the US, China and Russia still like them. You can plant a landmine in a second, and two generations later it can blow up your grandson.

I visited Cambodia some years ago, and in the landmine museum there, one of the awful facts I learned is that the Khmer Rouge would train fighters (who by the end were often children as young as 10) that if they were mortally wounded, they should go and plant a landmine somewhere secret and then die with that knowledge. This level of hostility toward other humans can't really be understood by even vaguely normal people.

The whole landmine museum, which helped to fund landmine removal, had been founded a child soldier from the Khmer Rouge who survived and wanted to atone. He had defused an incredibly large number of mines himself, and they had a huge collection of the casing of the ones he could salvage, only about 10-15% of the total, divided by country of origin, in stacks above your head.

(And some older Canadian couple had financed it and were deeply involved too. They weren't mentioned much if at all in the museum, but you saw them in the pictures, and there was a "family tree" off in a corner that had pictures of everyone working in the museum, descending by age like a tree, with these old cheerful Canadians at the top! I never learned their name, but good for them.)