My first attempt at something like this, basically to work my way around a writer's block. English is not my native language and I do not have a Beta, be warned!
The title and lyrics are by The Eagles. I do not own anything from Supernatural or the song. Just borrowing!
Despite appearances, this is not a Deathfic.
Learn to be still
Though the world is torn and shaken
Even if your heart is breaking
It's waiting for you to awaken
And someday you will
Learn to be still
The Eagles
"It's the only way," muttered Sam, his slightly dazed eyes focussed on his brother.
"Sam, what…"
Dean's eyes widened when Sam raised his gun to his temple.
"It showed me, Dean. Only one of us can leave." His eyes were still on Dean's face, willing him to understand. The gun was heavy and cold in his hand. "The only way," he said again. "You or me."
Dean ran forward to stop him, but Sam was faster.
The only way.
He pulled the trigger.
Dean caught him before he hit the ground, his eyes still open and staring without focus at his brother's face.