I can't believe Avgas is the cause!
EIO, auto-feather issue, VMCA, is far more likely but only speculation.
You find yourself loosing an engine shortly after VR close to vmca , auto-feather may or may not work in time and having to pull the other power level, lowering the nose to stop the roll only means you're going to sink, poor vis and a lack of altitude and I fear you can do everything by the book and it may still not be enough..
A very sad day and brings home how fragile life is...
RIP