There are cases where a few devices catch fire due to some isolated reasons. This too can be an isolated case. The viral video appears to be an exaggeration of a normal incident.
Live....and Let Live!
As our common sense says, it could be a short circuit case, as the news says clearly that it was on charging.
Nowadays, everything that is shown on social media carrying something different, goes viral, and people are over reactive about such incidents. A smartphone is also an electronic gadget and it might behave the same way, as any other gadget does, when all the aspects are not right. It too should be treated carefully, as we do with other gadgets.
I too second what Timmappa says, that it has nothing to do with the Samsung incidents, as there were a whole lot of handsets coming up with the same complaint, and here it is a single, individual case so far.