The Bureau of Investigation and local police investigated the case for over three years without success . Occasional arrests garnered headlines but each time they failed to support indictments . Most of the initial investigation focused on anarchists and communists , such as the Galleanist group , whom authorities believed were involved in the 1919 bombings . During President Warren G. Harding 's administration , officials evaluated the Soviets as possible masterminds of the Wall Street bombing and then the Communist Party USA . In 1944 , the Federal Bureau of Investigation , successor to the BOI , investigated again . It concluded that its agents had explored many radical groups , " such as the Union of Russian Workers , the I.W.W. , Communist , etc. ... and from the result of the investigations to date it would appear that none of the aforementioned organizations had any hand in the matter and that the explosion was the work of either Italian anarchists or Italian terrorists . " One Galleanist in particular , Italian anarchist Mario Buda ( 1884 – 1963 ) , an associate of Sacco and Vanzetti , and the owner of a car which led to the arrest of the latter for a separate robbery and murder , is alleged by some historians , including Paul Avrich , to be the man most likely to have planted the bomb . Avrich and other historians theorize that Buda acted in revenge for the arrest and indictment of his fellow Galleanists , Sacco and Vanzetti . Buda 's involvement as the Wall Street bombmaker was confirmed by statements made by his nephew Frank Maffi and fellow anarchist Charles Poggi , who interviewed Buda in Savignano , Italy , in 1955 . Buda ( at that time known by the alias of Mike Boda ) had eluded authorities at the time of the arrests of Sacco and Vanzetti , was experienced in the use of dynamite and other explosives , was known to use sash weights as shrapnel in his time bombs , and is believed to have constructed several of the largest package bombs for the Galleanists ( Buda was also a suspect in the Preparedness Day Bombing of San Francisco July 22 , 1916 ) . These included a large black powder bomb that killed nine policemen in Milwaukee , Wisconsin in 1917 . Buda was in New York City at the time of the bombing , but he was neither arrested nor questioned by police
Preparedness Day Bombing
Preparedness Day Bombing
Wall Street bombing