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Death toll climbs as Russia holds day of mourning for terror attack victims

Moscow fell silent as Russians, joined by President Vladimir Putin, held a national day of mourning for the victims of Friday’s terror attack at a concert hall. It was the deadliest terror attack Russia has seen in 20 years, as the death toll rose to at least 137 people. While ISIS claimed responsibility for the attack, President Putin repeatedly implicated Ukraine. NBC News’ Matt Bradley reports.