Steve Buress is a 60-year-old man and retired G.P. who became possessed by the ghost of Chester Johnson when he put on a clown costume. The costume was intended to be used for playing dress-up with his grandson, however, the ghost took him to the hospital to kill Phil Evans and nearly Sam Winchester.
He was freed from the possession when Sam touched him with an iron spike, which scared off Chester and enabled Sam to remove the mask. Steve was utterly confused, not even aware how he got to the hospital. Due to the nature of the crime, Sam allowed him to "escape".