about half an hour into the parade, a time bomb in the form of a cast steel pipe filled with explosives detonated on the west side of Steuart Street, just south of Market Street, about 450 feet from the Ferry Building. Before capping the steel pipe containing the explosive (believed by police to have been either TNT or dynamite), the bomb-maker had filled the pipe with metal slugs designed to act as shrapnel, greatly increasing the bomb's lethality. Ten bystanders were killed and forty wounded, including a young girl who had her legs blown off. The bombing was the worst terrorist act in San Francisco history. Witnesses differed on where the bomb was located. Some witnesses stated that they saw a man leaving a suitcase against the corner of a building at Market and Steuart streets that contained the bomb, while others, such as Dr. Mora Moss, testified he saw the bomb being hurled or dropped from the roof of a nearby building, rather than being left at the scene. Trials and convictions Led by San Francisco District Attorney Charles Fickert, authorities initially focused their attention on several well-known radicals and anarchists in the city, among them Alexander Berkman, who was well known to the government for his radical politics and prior conviction as an attempted assassin. He had only recently relocated to San Francisco after being implicated in yet another bombing conspiracy, the Lexington Avenue bombing in New York City, which resulted in the deaths of several anarchists and at least one innocent bystander. While in San Francisco, Berkman had begun his own anarchist journal, which he named The Blast. After the Preparedness Day bombing, Berkman abruptly abandoned The Blast and returned to New York, rejoining Emma Goldman to work on the Mother Earth Bulletin. Fickert attempted to have Berkman extradited back to San Francisco on conspiracy charges related to the bombing, but was unsuccessful. Two known radical labor leaders – Thomas Mooney (ca. 1882–1942) and his assistant, Warren K. Billings (1893–1972) – were eventually arrested. Billings, convicted previously for carrying dynamite on a passenger train, had a reputation for enjoying direct action; and Mooney, a militant socialist, had been arrested but never convicted for conspiring to dynamite power lines during the 1913 Pacific Gas and Electric Company strike. Mooney and his wife had also previously been arrested for unsuccessfully attempting to stop streetcar operations during a planned streetcar