You beat me to it.
The communication may have gone something like this:
Beane calls Murray's agent: "Hi, this is Brandon Beane, GM of the Buffalo Bills. I'd like to find out if your client, DeMarco Murray, would have any interest in joining our team."
Agent: "Let me find out and get back to you."
Agent contacts Murray: "DeMarco, I just got a call from the Buffalo Bills asking if you'd be interested in joining them."
Murray, knowing the Bills had two of their top offensive linemen retire and question marks at the QB and WR positions: "What?! Hell no!! Tell them I retired!"