(bbm)Welcome to WS,
elannia. Nubes are are always welcome -- especially when they come with good questions and a sincere desire to understand how this tragedy happened.
About the bbm... There are threads where the 911 call is discussed in detail. When you feel at home here, you might want to explore some of the older threads. I'll give you my explanation of the meaning (others may disagree). First, you have to understand that for Burke to even ask the question on the 911 recording, he had to have been in the room despite earlier Ramsey denials of it. I believe his voice is not only heard at the end of the recording, but at the beginning as well.
IF he knew about her death at that point, and
IF the RN was staging created by either one of the Ramsey adults, he wouldn't know what a ransom note had to do with JonBenet's death.
IF the parents didn't explain the details of what they were doing to protect him, he might think he'd wait until his mother hung up the phone (they thought) and ask about overhearing her tell the 911 operator that they found a ransom note. My understanding of the conversation (there are conflicting reports) revealed by Aerospace enhancement went something like this:
Burke: What did you find?
John: We're not speaking to you.
Burke: Well ( or "But") what did you find? (This would explain why some accounts say their was an emphasis on the word "did".)
I can give you file links so you can hear the recordings for yourself if you don't know where to find them.