Friday evening, Moscow time, four or five armed men strolled into the Crocus Concert Hall in northwest Moscow and opened fire on the crowd. Before departing the area they had killed at least 40 people and wounded over 100 more. My colleague, Ward Clark, has some good observations; the only one I'd add is that at least two of the attackers had trouble managing magazine changes. While Dmitry Medvedev, deputy head of the Russian Security Council, hinted that Ukraine had been behind the attack and threatened to commit atrocities that the Russians have failed to commit so far should Ukraine...