The movie stars Joseph Cotten, Rhonda Fleming, and Wendell Corey. I reviewed the film in the fall of 2009.
There's more on this film at 50 Westerns From the 50s. Incidentally, it can currently be watched via Netflix streaming.
THE KILLER IS LOOSE is listed at TCM and Screen Archives Entertainment, but as of this writing it does not yet have an Amazon listing.
Other titles due soon from MGM: GUN DUEL IN DURANGO (1957) with George Montgomery and Ann Robinson; QUINCANNON, FRONTIER SCOUT (1956) with Tony Martin and Peggie Castle; THE HALLIDAY BRAND (1957) with Joseph Cotten; and DOWN THREE DARK STREETS (1954) with Broderick Crawford and Ruth Roman.
Most of these films are currently available to watch via Netflix "Watch Instantly."