Sorry for your friend. I have lost several friends to aviation as well. I investigate and settle aviation claims for a living and it is almost 100 percent the guy with the stick in his hand. Mechanical failures, while not unknown, are rarely the causes of fatal crashes. Most are slow/stall/spin in the airport environment. You guy might have PPC time, but I'd be curious to know what kind of regular AC time/training he had. RIP.