Critics, including Beslan residents who survived the attack and relatives of the victims, focused on allegations that the storming of the school was ruthless. They cite the use of heavy weapons, such as tanks and "Shmel" rocket flamethrowers. Their usage was officially confirmed. The "Shmel" is a type of thermobaric weapon, described by a source associated with the US military as "just about the most vicious weapon you can imagine – igniting the air, sucking the oxygen out of an enclosed area and creating a massive pressure wave crushing anything unfortunate enough to have lived through the conflagration." Pavel Felgenhauer has gone further and accused the government of also firing rockets from an Mi-24 attack helicopter, a claim that the authorities deny. Some human rights activists claim that at least 80% of the hostages were killed by indiscriminate Russian fire. According to Felgenhauer, "It was not a hostage rescue operation... but an army operation aimed at wiping out the terrorists." David Satter of the Hudson Institute said the incident "presents a chilling portrait of the Russian leadership and its total disregard for human life".