Harry Horowitz (c. 1889 – April 13, 1914), also known as "Gyp the Blood",[2] was an American underworld figure and a leader of the Lenox Avenue Gang in New York City.

[1] New York City Judge Franklin C. Hoyt later recalled: Three or four years ago, when I was sitting in special sessions, my associates and I had occasion to sentence a young man who had been found guilty of petty larceny.

In pronouncing sentence I said: 'I am convinced from the evidence that has been brought out here that you are lacking in moral sense, that at the end of your prison term you will go out and commit more.

Two of the killers, Jacob Seidenshner (aka "Whitey Lewis"),[6] and Francisco "Frank" Cirofici (aka "Dago Frank") were arrested immediately after the killing, along with Charles Becker, a detective from the New York Police Department who was suspected of being a business partner of Rosenthal,[7] but Horowitz and the fourth gunman, "Lefty" Louis Rosenberg, were not.

[12] They produced additional witnesses on April 11, 1914, who swore to their innocence, but New York Supreme Court Justice Goff did not find them credible.

[13] Horowitz gave a last statement to the press on April 13, 1914, stating: We all knew that the result was decided against us just as soon as we heard Justice Goff was in the case.

Cirofici made the statement in the presence of the warden, the superintendent of the State Prison Department, and his mother and sister, regarding Rosenthal's murder.

Blues singer Richard "Rabbit" Brown wrote a song called "Gyp The Blood", which appears to be based on him.

A character nicknamed Gyp the Blood appears in a book by Kevin Baker, where a fictionalized version of events from Harry Horowitz's life play out.