A mastermind of the May 3 deadly terrorist attack in Dagestan’s capital city of Makhachkala was killed in a special police operation early on Wednesday, Russia’s National Anti-Terrorism Committee said. Hussein Mamayev, the leader of the so-called \"Makhachkala\" gang, was surrounded in a building under construction in the outskirts of Makhachkala. \"The bandit refused to surrender and offered armed resistance,\" the committee said in a statement. \"He was killed by return fire,\" added the statement quoted by Russian (RIA NOVOSTI) news agency. Police seized a Kalashnikov assault rifle and a handgun at the site. A car bomb went off near a police checkpoint on the outskirts of Makhachkala on May 3 and another blast occurred in a Gazelle minivan shortly afterward. The explosions killed 13 and injured at least 100.