At least 40 people were killed and more than 100 were injured after armed attackers stormed a popular concert venue complex near Moscow and opened fire, according to preliminary information from the Federal Security Service in Russia, state media TASS reported.
Even if you assumed that the US had absolutely nothing to do with this, having intelligence and other sharing it is absolutely it’s own complicity.
The US used 9/11 as the pretext for two totally unrelated wars and global military actions.
Imagine what they’d do if Russia had known about it in advance and just sent a smug tweet.
It’s quite possible they did share, but the Russians thought they had it handled. Afaik there was a mirror situation in 2013 with the Boston bombings, Russian intelligence knew about the terrorists and tipped off the CIA but was largely disregarded.