I'm not surprised something like this has happened, and I do feel sorry for that poor woman and her family. It must have been horrific and frightening, not to mention excruciatingly painful.
However access to petroleum is tightly controlled for a very good reason. It's a highly flammable substance and needs to be stored properly.
It may be 'common sense' to a lot of posters on this thread but as this awful incident illustrates, it isn't to everyone. You cannot assume that people know these things, you have to tell them.
Also, with regard to storing it in your shed (should you have one of course)...what if you did something without thinking and your shed caught fire? Fire spreads incredibly quickly.
Bearing this in mind, there's no way in hell anyone should be storing it on the balcony of a flat. You might think, well I know how to store it, don't put it near a heat source what a load of nanny state nonsense blah de blah but all it takes is one mistake/lapse in judgement.
That's why people shouldn't be storing petrol.