So, Connie probably learned of Carlo's murder through notification by the authorities. Her reference to the papers was probably a general one since Michael's position as a Don would have been grist for the newspaper mills.
Well, that raises an interesting point. As Oli notes, Connie's "hysteria" comes
after the actual murder--perhaps several days or even weeks. What was she told about Carlo's disappearance in the interim? What did she think?
I'm
guessing that she was told that Carlo went off to Vegas as was planned before Michael said to Carlo (alone), "Can't go to Vegas, Carlo." His failure to contact her might have seemed to her as if he'd lapsed back into his old, philandering mode--until she read the papers. The papers would have been full of news of the Great Massacre of 1955. They
might not have associated Michael with the massacre because Vito had died and Michael had kept a low profile. But Connie knew Michael was behind the massacre, and figured out what happened to Carlo.
