The threats, reportedly, came from people connected with the infamous Chicago mob. Calabrese, Jr., has a new book out entitled "Operation Family Secrets" that outlines his time as a key witness against the mob during which he testified against his own family. Both stores, and the author, received threats that the stores felt were too serious not to cancel.
The story has been reported on various Chicago media outlets. The first store was in suburban Oak Brook, who received phone calls from purported mob participants who warned against having a "rat" at their store. The next store to cancel was the Borders bookstore located in downtown Chicago who, reportedly, received similar threats.
Calabrese has appeared on local television news saying that he agreed to the cancellations because he does not want anyone who might attend to be hurt. However, not every store where he was scheduled to sign has canceled. He still has signings scheduled at Elmhurst College, the Arlington Heights Memorial Library and the Union League Club.
Calabrese was a key witness against his own father and uncle in the Family Secrets mob trial that electrified Chicago several years ago. His testimony was key in securing convictions against key mob figures for murder and conspiring to murder other mob members.