I bet it was a dispute over someone illegally poaching walleyes. I've seen people attempt to poach but have never confront them.
Now I frequent that as area almost every year for white bass fishing, and I can attest to how rude Hmong boaters are. You catch one fish and they come and drop anchor right where you're fishing. And since their boat is probably over occupants capacity, they tend to have advantage of crowding lines in the area so one can no longer even make a cast without tangling lines. Of course they also have to talk in Hmong talking shirt as if I don't have a clue what they're saying. But fobby accent smack talking, it's not difficult to figure that out. And of course the would always on purpose rev the propeller when they near you just to be annoying.