Huge SPN fan that's watched every episode and most all episodes 2-4 times. Lol. Jack did a mercy killing on a snake. (Snakes are a reference to evil in the Bible ya know but that's actually besides the point.) Dean flips the flip out that Castiel didn't tell the brothers that Jack is struggling with things inside his head. The Winchesters has been struggling with "inner voices" and/or "inner demons" for years and most times keeping them from each other over and over and over again. Jack didn't completely lose it until after he killed Mary because he knew he hurt the brothers. I simply can not understand why the writers/producers had Dean being so hard on Castiel especially how loyal he's been ever since he exploded after taking in all those souls years back. Yes, Jack did kill Mary and Dean shutting out Castiel the way he did still today makes no sense UNLESS they ran out/couldn't think of a direction to take after Mary's passing. Again.