Here is something I found this morning:
On the 16th September 1920 a bomb went off in Wall Street killing 38 and injuring 143. The bomb was in a horse drawn carriage and contained 100lbs of dinamite and 500lbs of cast iron weights. The horse and carriage were shredded and those that did not die instantly, suffered horrible wounds. They were for the most part young workers, many of whom were low paid.
The bomber is thought to have left the scene prior to the explosion, thus surviving, yet no one was convicted despite much investigation. It is thought to have been placed by Italian anarchists, known as Galleanists. The main suspect, Mario Buda, was believed to have returned to Italy. The group remained active in the US and also set off a bomb in 1932.