Italian and American police suspected Czolgosz was tied to L’Era Nuova (New Era), the same anarchist group as Gaetano Bresci, assassin of Italian King Umberto I. Bresci had been involved with this group and related groups such as Gruppo Diritto all’Esistenza (Right to an Existence Group) in Paterson, New Jersey, which was a center of the anarchist movement and became an active center for the Industrial Workers of the World (IWW), one of the predecessors of the future Communist Party USA.
Thanks for adding to that.