The Barrel Murder by Michael Zarocostas
Based on true events, The Barrel Murder traces the NYPD's investigation of the April 14, 1903 barrel murder, in which a man was found stabbed to death, dismembered, and placed on display in a barrel in Little Italy. Two NYPD outcasts hunt for the killer: Detective Joe Petrosino (a stocky "Dago" nicknamed Bulldog Joe) and Inspector Max Schmittberger (a giant "Yid" nicknamed The Broom).
Commissioner Teddy Roosevelt appointed Petrosino the first Italian-American detective in the NYPD and reinstated Schmittberger after The Broom confessed to grafting and blew the whistle on his fellow cops. By 1903, however, Roosevelt is in the White House, and Tammany Hall casts a long Irish shadow over the NYPD again. To complicate matters, investigative reporter Lincoln Steffens seeks Petrosino's help in finding out if there is a crooked lawman behind a gambling syndicate in the City.
As they work the barrel murder, Petrosino and Schmittberger encounter a lunatic doctor, the Secret Service, vicious Sicilian mafiosi known as the Morello Gang, and a mysterious code that may unlock the secrets of the killing and Steffens' alleged syndicate.
Note to the reader: This novel is based on an actual murder that occurred in New York City in 1903 and the criminal investigation that followed. Several of the main characters are real persons or inspired by real persons. Joe Petrosino, the central character, was the first Italian-American detective in the NYPD's Central Bureau appointed in 1895 by Teddy Roosevelt (then President of the Board of New York City Police Commissoners). Petrosino and a few other brave men protected the immigrant masses and fought against the most feared criminals in the city's history. Their story begins here.