This was the most audacious hit in mob history and this was why the feds had such determiniation in getting John Gotti. A high profile mob hit during rush hour isnt supposed to happen. There were thousands of people leaving work and Christmas shopping and someone could have taken a bullet. There almost was a “ how can you have let this happen” attitute towards the FBI back then. Gotti certainly didnt help himself by basically saying “ yeah I did it, now go and prove it”.
The FBI immediately noticed men walking up to Gotti amd showing deference towards him. Thats when they knew he had something to do with the hit since was wasnt part of the administration prior to Castellano’s death and not somone considered next in line to the thrown.