He is located on the Stadium field along with Carol Dawes. He tells players that he, along with others, were brought in from the Union City South Hospital and that he had went there to look for his brother, who was in a coma at the time. He found the place infested with zombies and his brother torn to pieces. The Military then arrived and brought the survivors to the Stadium.
Steve's story about his brother is likely a reference to Rick Grimes of "The Walking Dead" comic book/TV series. Both characters fell into comas and placed in hospitals sometime before the zombie apocalypse, however the stories vary slightly; Rick awakens from his coma whilst Steve's brother is killed.