Sorry to hear about that, but don't put any blame on your uncle. One (seemingly) harmless action can result in a situation like that.
I was once involved in a bad road rage incident. Traveling on 140S in Taunton, approaching the Target/Home Depot, a Ford Bronco attempts to pass me in the breakdown lane. I move over a little to block him, and that's where everything started. He passes me by violating the double yellow, I stop. He stops, backs up, and approaches my car. I safely drive by him and his truck, and he follows me.
I take a bunch of back roads I know, trying to get to the closest police station that I know of (Raynham). As we're a few miles out, he passes me again on a small road, parks in the middle, and I pull into a dirt lot to try to get away. He gets out, approaches my car, and I remained there as I didn't want to run him over. He starts yelling at me, punches the window (left it closed, doors locked), then leaves after yelling again.
The best part is his reason for being pissed at me. People like me are "responsible for the death of his nephew". All I did was block his illegal pass. While he was telling me that, he left his toddler in the truck parked in the middle of the road (awesome dad). Police showed up, nothing can be proven so no charges, but the cop told me where he lived (my now-wife and I both memorized his plate). Of course I did nothing to return his nice behavior, not worth ruining my life.
Maybe your uncle followed my "rule" on merging, one car from left, one from right. Maybe Erik wanted to break that rule.