John and the boys run into the alley and while Sam wants them to stay together, Dean knows it's safer if they stay apart for now. They're all pretty bloody in this scene.
DEAN: Wait, wait, wait! Sam, wait. Dad, you can’t come with us. SAM: What? What are you talkin’ about? JOHN: You boys-you’re beat to hell. DEAN: We’ll be all right. SAM: Dean, we should stick together. We’ll go after those demons- DEAN: Sam! Listen to me! We almost got Dad killed in there. Don’t you understand? They’re not gonna stop. They’re gonna try again. They’re gonna use us to get to him. I mean, Meg was right. Dad’s vulnerable when he’s with us. He-he’s stronger without us around.