The proper response is the Potemkin Gambit; wherein the Russians first show compassion by holding a trial with full rights for this particular scumbag in such a way that everyone in the world is impressed by how fair the Russians are being.
This will have the effect of shaming radical Muslims worldwide.
In the meantime, Putin's Intel is verifying the regions of the world that had the most to do with this war crime.
Upon the final guilty verdict in the trial, punishment is then meeted out to every tainted region in the world.
This carries an added psycological injury with it because of the earlier humanitarianism shown by giving full rights to the defendent at his trial...along with preventing large numbers of future terrorists from being able to repeat such madness (due to the Mecca Delenda Est treatment).
To that end, I've already read on-line that Putin has called for mobilizing 500,000 Russian troops.
War is coming.
5 Legislative Days Left Until The AWB Expires