Addon to this.
American and Russian (Soviet) arms have been killing the opposition for decades. Both sides open sell arms to adversaries of their opponent. Ukraine is using American bombs to kill Russians right now.
Just because something was made in a particular area mean its an act of war from that area.
Part of this is the result of arming a bunch of militia on both sides. They are going to use those weapons in ways they see regardless of the 'rules of war' established by both sides.