Dean looks down at the gun in his hand.
He thinks about all the times it's been of use to him. How ironic. The gun that has saved his life a hundred times over is about to end it.
He flips it over in his hand and checks the barrel. Loaded. Ready.
But is he?
He wrote a letter to Sam. After all they've been through, it isn't much. But he wrote it anyway; he couldn't just go without saying goodbye, even if it isn't face to face.
Dean is much too ashamed for that.
But what can he say to Cas? There's nothing he can think of to leave the angel as a proper thanks. There's that, and there's the fact that he's ashamed of what he's about to do. It's throwing everything Cas had done for him back in the angel's face.
Hey, thanks for saving me from Hell and all, but I'm gonna kill myself now.
He isn't even sure if it will work. In his experience, dead things don't stay dead.
He takes the gun, and raises it to his throat with a shaking hand. C'mon, keep it together, he tells himself. He steadies his hand and hesitates. Taking a breath, he closes his eyes and puts his finger on the trigger.
"I'm sorry, Cas."
He breathes the words and pulls the trigger.
The sound of a gun.
A gust of wind.
"Dean!" Castiel shouts, a millisecond too late.