Those guys, Roy and Walt must be some of the stupidest Hunters ever. (either that or Cas took them out while Sam and Dean were dead, both are equally likely)
So you're Hunters and you kill two guys, two other Hunters, one of whom you kill for starting the apocalypse, and the other to keep him from hunting you down for it. And the one you know will come after you for killing his brother, tells you right before he dies, that when he gets back, he'll be pissed.
And you DON'T FREAKING SALT AND BURN THEIR REMAINS?
How stupid can you be?
I halfway expected the boys to wake up on a pyre and then kick the crap out of those guys...