"Prominent critics of the Kremlin, and Putin in particular, seem to have a terrible habit of dropping dead under very suspicious circumstances. Some fall out of windows, bludgeon themselves to death, are poisoned or are said to have committed suicide in ways that defy logic.

Anonymous US intelligence officials have long said they suspected that some of the mysterious deaths over the years were part of a campaign by Putin to assassinate his enemies. But internal US government documents that contained such explicit assertions have never really surfaced.

Until now."