I think I can explain why that happened.
Our countries here are a bit different than the West. Those guns were never meant as a defense against some totalitarian government, which is the usual Western/American motivation. Those guns were meant to serve as a defense against Ustase Croats (is Serbia's vision) and Muslim Bosnians, i.e. ethnic threats. To see kids fall prey to them was heartbreaking and completely unexpected for the area, shootings are very, very exceptional here, and some degree of safety is expected.
Also the weapons are a reminder of a war that most Serbs think as fratricidal and an unnecessary tragedy, and want nothing to remind them of it.
We don't trust our governments either, in fact we're likely far more suspicious than Americans, due to corruption and communism's legacy. But we also don't want to civil war overthrow them and shed the blood of our co-ethnics. At least those that are still sane, cause there is more and more insanity here too, sadly.
Still, considering how unstable the world is getting, I would've preferred they kept the guns, although it would've been nearly impossible to make this case in the heat of the moment.