Ah I see.... for an article about a covert investigation it sure assumes intimate knowledge of the covert investigation

They describe how they got the info in the original article, and then deduced the rest. They called to confirm the suspcicions, which were already enough by themselves. They got lucky that the details were sufficient to make the killer think he really talks to someone from his office.

I think CNN is just assuming their readers aren't going to ask questions like yours.

It happened in the same hour, both were made at 7AM local time.