From https://t.me/pravdaGerashchenko_en

According to one of the versions, the shooters in #Russian Derbent and #Makhachkala might be related to international terrorist organizations, #Russian #RBK media reports, and citing a source in the law enforcement agencies of #Dagestan

Judging by the actions of the shooters, their shouts, and appearance, the terrorists might belong to an Islamist terrorist organization, the source said.