Law enforcement officials are concerned about the possibility of radical groups in the United States responding to ISIS's calls for similar attacks following a recent deadly terrorist incident at a concert hall in Moscow. A U.S. intelligence bulletin has warned that ISIS operatives globally, as well as so-called "lone wolves," could be motivated by recent statements from the terrorist organization praising the Moscow attack and urging further attacks on public venues, even if these individuals are not affiliated with ISIS.
The attack in Moscow on March 22 at Crocus City Hall resulted in the deaths of at least 144 people, including three children, and left at least 550 others injured. Following the incident, Russian authorities arrested nine suspects from Tajikistan after gunmen used automatic weapons to open fire on concertgoers and then set a fire that engulfed the complex.
In a statement released after the attack, ISIS claimed responsibility, stating that their fighters had targeted a "large gathering for Christians" in the Moscow suburb. The United States reportedly shared intelligence with Russia weeks before the attack, warning of potential similar assaults on concerts in Moscow. The U.S. State Department stated that it had shared information about a possible attack with Russian authorities as part of its "duty to warn" policy
On March 7, the U.S. Embassy in Moscow issued a warning advising U.S. citizens to avoid large gatherings for 48 hours, citing "imminent plans" by extremists to target such events in Moscow.