"You don't have to."
"Yes, I do."
And Dean knows he'd say that.
Fucking knows.
He's not even sure why he gave Sam the choice.
He blames himself for a while.
If he'd have killed her back at Kurt's, Dean wouldn't even be stood here.
And neither would Sam.
"Please."
And then there's this look on Sam's face, and it's just so Sam, and it's agonizing.
Dean knows Sam wanted to save her. Wants to save her.
But is it worth losing himself in the process?
He knows she asked Sam to do it.
And that right now, he should definitely not be handing Sam his gun.
But somehow he knows Sam has to do this.
"Just wait here."
Dean's not really listening anymore.
He just wants to go back. Erase that look from Sam's face, the one that screams it shouldn't be like this, and he knows Sam is right.
He never wanted this for Sam.
He's thinking that he remembers stories from when he was young, where his dad told him of brave hunters, like you and Sammy, who hunted evil werewolves.
But it's not like that anymore.
There's nothing left right now.
No good or evil, right or wrong.
There's just Sam, and Dean, and this room.
And certainly no happy ending.
He has nightmares afterwards.
Sometimes in the night, sometimes in the day.
In the end, he can't tell which is memory, which is dream.
Sometimes, the room is different.
Sometimes he's watching himself, his actions, from somewhere behind Sam. Wants to scream at himself, take the gun and throw it as far as he can.
Shapes shift and blur, and suddenly he's back there, in that moment.
Sam's turning, and walking out the door. Turning, he looks at Dean.
And Dean sees a flash of something in his eyes, just for a second.
Something that resounds in his ears like sorry, until he's left wondering if he's saying it, or if Sam can even hear him.
Sam blinks, and everything swims in tears again.
Sam moves forward, out of sight, and suddenly Dean can't see.
There's tears, stinging his eyes, blurring the room around him, making him choke.
Something dawns on him, and he realises it's too late.
Realises that Sam just left, and he's not coming back.
He just won't be the same anymore.
There's only so much darkness can spill into the soul before everything turns black.
He stares at the empty doorway, and a single tear finally falls, but he doesn't acknowledge it.
He wonders how he got here.
How this happened.
Wonders if he'll ever see Sammy in Sam again.
Everything blurs, and he wonders if he's dreaming.
There's dark noise, screaming in his ears.
He's going to cry out, to stop Sam, but knows it's too late.
Thinks, maybe we were both lost a long time ago.
There's a sudden silence everywhere.
Like he knows what's coming.
Like he knows it's the end.
He expects the bang, but it still makes him flinch.
And just like that, everything is gone.
There's no happy ending, and Sam dies in that room in San Francisco, years away from the home he never had, along with what little was left of Dean Winchester.