On July 22 , 1916 , a bomb exploded during the San Francisco Preparedness Day Parade , killing ten people and wounding 40 . Police suspected Berkman , although there was no evidence , and ultimately their investigation focused on two local labor activists , Thomas Mooney and Warren Billings . Although neither Mooney nor Billings were anarchists , Berkman came to their aid : raising a defense fund , hiring lawyers , and beginning a national campaign on their behalf . Mooney and Billings were convicted , with Mooney sentenced to death and Billings to life imprisonment
a bomb exploded
Preparedness Day Bombing
Alexander Berkman