I think this happened loads. Especially if it was a made man that was whacked and the killer was in the same family/crew. If they wanted Feds to think it wasn’t a family sanctioned hit they would attend. Same if they wanted to deflect blame away from the family to other members.

Obviously both the feds and other mafioso know who really done it every time anyway haha. Any Mafia guy gets hit 95% of the time it’s by their own family.