Carroll John Daly 
The Snarl of the Beast [EPUB ebook] 
Race Williams #17 (Black Mask)

Who is the criminal known only as “The Beast?” Too baffling for the police to solve, it becomes a manhunt in which detective Race Williams must track down “the most feared, the cunningest and cruelest creature that stalks the city streets at night.” But it will soon become Race’s most dangerous case as he tries to stay alive. One of the longest and best of the dozens of Race Williams adventures. Story #17 in the Race Williams series.
Carroll John Daly (1889–1958) was the creator of the first hard-boiled private eye story, predating Dashiell Hammett’s first Continental Op story by several months. Daly’s classic character, Race Williams, was one of the most popular fiction characters of the pulps, and the direct inspiration for Mickey Spillane’s Mike Hammer.