I love you so much. My baby brother.  He then makes Sam promise that it'll be OK, so Sam lays his hand over Dean's and says, It's OK. You can go now.  Goodbye, Sam  are Dean's final words as his hand drops and a tear rolls down his cheek.

Sam's supernatural abilities are the result of him being fed Azazel's demon blood while he was an infant. Sam exhibits signs of precognition throughout the first season, manifesting as dreams of others' deaths and later as visions.