I've just seen that video earlier today as it happens. Well i saw a gif of the apparently casual murder 1st then the fuller video with description.
It does at 1st appear to be a deliberate act of callous murder, but on closer inspection and the details given it does seem to be an accidental discharge on draw of weapon and then him trying to work out i f he can cover up his blunder.
http://www.liveleak.com/view?i=5cf_1449814783#7ayjhoOVUuaPTRHe.16