Here's a quote worth pondering:
Someone with access to fresh Polonium 210 (read: less than a year old, hot from the reactor) decided to use it to bump off an enemy. And the terrorism alert status hasn't risen a notch? Pull the other one.
If Putin ordered the hit, it means we have a head-of-state prepared to use nuclear material to kill enemies, and spread it globally. If someone in the Russian nuclear network did it without Putin's permission, we have an even bigger problem on our hands. Here we were worried that Saddam could hand off nuclear material to rogue actors. And we didn't think of Putin.