Some historians have also suspected the Galleanists of perpetrating the Preparedness Day bombing in San Francisco on July 22, 1916. No known Galleanists were among those indicted for the attack, but the time bomb's design and construction – a cast steel pipe packed with explosives, a timing mechanism, and metal slugs designed to act as shrapnel and increase casualties – was typical of later Galleanist bombing campaigns, the work of Mario Buda in particular. Additionally, in an ominous apparent reference to the earlier mass poisoning by the Galleanist Nestor Dondoglio, San Francisco police recovered two unsigned letters urging the headwaiter at the St. Francis Hotel to poison soup served to Police Commissioner James Woods, one of the organizers of the Preparedness Day march.Bomb Hurled Through Air, Says Physician Who Was Witness to Saturday Outrage, Reno Evening Gazette, 24 July 1916, pp. 1–2
