The findings from five European governments that Kremlin critic Alexei Navalny was killed with poison are “troubling,” U.S. Secretary of State Marco Rubio said on Sunday. France, Germany, the Netherlands, Sweden and the United Kingdom said on Saturday that Russia poisoned Navalny with a toxin from a poison dart frog, leading to his death in a penal colony two years ago. Moscow dismissed the accusation. “We obviously are aware of the report. It’s a troubling report. We’re aware of that case of