RIP to the family and crew. This is so sad, mostly because it is 100% preventable. Just an FYI, when ever I see a crewmember using the O2, even if it is for unexplained reasons, like a headache or whatever, I am always glad. Not to mention the O2 system operational test and the pilot's functional knowledge. I'll get it serviced if it needs filling. I'm simply glad it is in regular use and they are comfortable using it!!!!!
I have the unusual distinction of having experienced a good number of depressurization events at FL450. There may be a few people in the world who have experienced more, but I am unaware of them.
While working for WR Grace, the 5 year old GIII would fully open the outflow valve in cruise flight. Since we were flying 3 round trips/week, we experienced this on almost every round trip, we had an extraordinary number of failures.
I will say, that it was not 'explosive' but rather a 8-10 second event as that's the outflow valve transit time. The motor was drawing too much current, and would 'fry' the TO-3 drive transistors, which would simply port current to the motor, resulting in driving it open. The DOM at the time was too cheap to purchase a new outflow valve, and instead got warranty on the shorted part. This insanity continued for some time, despite some angry words.
My mask went on fast, and 100% was immediately selected, although breathing is not easy, as air is only going out of the lungs, I'd get 2 breaths in as soon as I could (that's how I was taught). I'd then select 'manual' and close the outflow valve. Once the captain did not recover well and did a visual approach to the wrong airport!
You can't hear anything and you can't see any warning lights, as the cockpit fogs up for a bit. You have NO IDEA what's happened. I saved our lives multiple times, and saved my own life a few years later. As I was by then, darn good with that mask.
Just a note to single pilot operators, consider using the O2 while at altitude. Work out, ahead of time, a way to get it serviced at your destinations. The FBO will do it for you.