Looking for a specific AU fic that features Dean as a killer that has been traveling the country with Sam as a teenager (hence the underage tag). Sam doesn't like the killing, but Dean has convinced him it is necessary or something. I specifically remember a scene where the police have them cornered, and Dean puts a knife to Sam's throat and holds him hostage, but Sam isn't worried, eventually Dean kills all of the police and they escape. Pretty sure it was on tumblr, but I'm not 100%. Any help would be much appreciated!