Gentlemen, I believe a little compassion for the victim is in order. I've thought about the accident and have reconstructed what may have happened to cause this truly unfortunate and tragic incident.
What I believe occurred in this accident prior to the chambered round discharging, is not an extremely rare chain of events. It can happen to any of us.
What it is, is a failure to feed completely. In a semi-automatic action like the SKS, loading fresh cartridge is performed by the bolt carrier/bolt, which on travelling forward while driven by the recoil spring, strips a fresh cartridge from the magazine and pushes it into the chamber, the bolt face/extractor firmly clamped onto the rim of the cartridge head.
Normally the bolt carrier/bolt assembly has sufficient energy to carry out this function successfully as provided by the recoil spring. But a gun is a mechanical device subject to friction, binding or any malfunction which could prevent its parts, i.e. the bolt carrier/bolt from attaining sufficient velocity and energy to accomplish its function.
The cartridge may feed, yes, but due to insufficient bolt velocity, the extractor may not have caught on the cartridge head rim. The bolt will not be in battery and the trigger will not release the firing pin. The operator pulls back the bolt carrier handle, the chambered round will not eject, because the extractor did not engage.
The next round from the magazine is pushed up against the magazine lips, ready to be pushed forward by the bolt. Operator releases the bolt handle, intentionally or accidentally, waiting cartridge is stripped from magazine, which then speeds forward. Its spitzer bullet’s tip strikes the primer of the chambered cartridge, igniting its propellant which drives the bullet downrange.
The cartridge casing head, being totally unsupported, is blown off by approximately 50,000 psi pressure. We know what followed next.
Personally never experienced this with my own SKSs but can see the possibility of a similar chain of events happening, given enough rounds fired.
In case of any FTF, FTE, in any gun, I'll remember to always drop mag before doing anything.