Earlier quoted context omitted.
Oh yeah... like using Polonium to kill Litvinenko... this is all about sending a message.
Indeed, and the message was "I'm insecure about my position".
I'm also not sure it's plain insecurity. I'm sure there are people not too far removed from him who if they could, would try to get to him -however, he goes to extreme measures to ensure he neutralizes possible threats when identified --including relatives and "old hands".
Although, being such a tyrant (insecure as he might be) why doesn't anyone of the people at his core who live in fear for themselves and everyone else just go on a final mission against him? It's not like he's the only one armed --plus he'd have to remain awake 24x7.