USA: Pentagon spokesperson questions Russian claim of al-Adnani airstrike

Pentagon Press Secretary Peter Cook responded to reports that a spokesperson for the self-proclaimed Islamic State (IS, formerly ISIS/ISIL), Abu Muhammad al-Adnani, was killed in a Russian airstrike, during a press conference in the Pentagon Briefing Room in Washington DC, Wednesday.
Cook called the death of Adnani "a very good thing." He explained the key role that Adnani played in the militant group, and that he was directly responsible for recruiting foreign fighters. Cook said that Adnani was "responsible for encouraging attacks against the west, against civilians and military personnel in the west."
However, the Pentagon spokesperson refused to support the claim from Russia's Ministry of Defence that a Russian airstrike was responsible for the killing, saying, "we have no information to support Russia's claim that they also carried out a strike against Adnani."
Cook continued, stating that Russia spent most of its time in Syria "supporting and propping up the Assad regime," and claiming that the Russians have "not devoted much, if any, effort that we're aware of targeting ISIL's leadership." The Pentagon Press Secretary added that "we're not going to be satisfied simply to trust ISIL and the Russians on this when we go through our process."