Remember Godfather 2, and the bar scene where Pentangeli is about to be
murdered, Danny Aiello says "This is a message from Michael Corleone..."

What does he mean? Obviously, Pentangeli is going to be killed, and what
difference does it make to him who did it?

So, why does he say it? Is Michael involved in his death/murder?

Also, in Godfather 2 Michael says "Killed by someone close to us..." he
must mean Fredo. However, Fredo could not kill anyone (!) and who is that
other person? Also, as they fish the bodies out, we never know who those
peope were. (Were they part of Fredo's gang? If so, then how could
Michael, Rocco and Tom not know who they were?)

I have read the postings for the second question, but I am not satisfied with the responses that makes sense.

Maybe someone else can help....