At the time , the bombing was the most fatal single event in national law enforcement history , only surpassed later by the World Trade Center terrorist attacks on September 11 , 2001 when 72 law enforcement officers representing eight different agencies were killed . Those responsible for the 1917 bombing never were apprehended , but days later , eleven alleged Italian anarchists went to trial on unrelated charges involving a fracas that had occurred two months before . The specter of the larger , uncharged crime of the bombing haunted the proceedings and assured convictions of all eleven . In 1918 Clarence Darrow led an appeal that gained freedom for most of the convicted
World Trade Center terrorist attacks
September 11 attacks
Milwaukee Police Department