The note claimed to be found at these "terrorists'" place in the bottom photo of the link you posted goes: dedicated to blah-blah, kill to live and live to kill, signature not legible.

That is, the actual words "signature not legible" instead of what an FSB higher-up probably wanted to be an inscrutable scrawl masquerading as the signature. Some of these FSB guys come straight from a Monty Python sketch.