Earlier quoted context omitted.
Indeed, that's an assault rifle, predecessor to the M16. Only available as semi-automatic for civilian, if not modified. https://en.wikipedia.org/wiki/AR-15_variant I don't know how you American call that, but I'd consider that as war equipment.
I don't know how you American call that, but I'd consider that as war equipment. The rest of your comment is informative and adds to the discussion. Your parent is making a similar point, which you expand on. This last statement you add is can be read as inflammatory. Gun discussions are contentious enough as it is, particularly on the internet, and they all to often derail into all manner of increasingly flamewar to…
In most countries, this sort of equipment is definitely classified as war guns. You are prohibited from possessing one, let alone use it.
In the USA, it's more opened, some stuff you can buy, some stuff you can't buy, not sure where this one is. I believe it's being discussed in another thread here.
This has implications on the story. Knowing the kind of weapon and the local norms would give more context about the situation. Expect the police to react differently against a handgun and a military grade assault rifle (not the same type of individual on the other side either).
Judging by the "hundreds of rounds", it might have been modified to automatic or it's an old model.