I spent the last several years of my underground career as an electrician certified by WVMHST. The very first day I was being trained by the WV Mining Extension Service our instructor spent the entire day showing us graphic videos of electrocutions, reading us MSHA "fatalgrams" where men had been electrocuted, and he kept pounding in the point that you only get one mistake when working with electricity. It almost made me back out of the training but it left an impression on me that I never forgot.
A cardinal rule, at least according to WVMHST is that no work can be performed anywhere that power could possibly be present, that everything is locked, tagged, and tried. Anyone caught working without any of those conditions would have their certification revoked on the spot. As for me, I never worked on a circuit without testing it with a volt meter on top of all the other precautions.
In all the years I worked as an electrician we had two incidents - one where a 600 volt 3 phase circuit breaker exploded when the electrician tried to reset it. He wasn't wearing gloves and was at eye level with the breaker which resulted in him getting burns on his hands and face. The other was when a guy forgot about the "feed through" circuit and got into 12,470 volts and somehow survived. The only close call I personally witnessed was when another electrician didn't take time to read the wiring diagram and started working on a 120 volt control circuit without realizing the control transformer picked up its power on the wrong side of the visual disconnect. The 12470 feeding the transformer was off but there was still 120 running through the relays and ground monitors.Luckily and after some arguing with him I got him stopped before he got "bit".
The highest voltage circuit I ever had to work on was at a 38,000 volt sub-station.........I was nervous as a whore in church even though I knew it was de-energized
As for your friend...........I'm sorry for your loss. I can't imagine what it would be to walk in on something like that.