BRIAN STELTER (HOST): Unfortunately, two stories have merged this weekend. The pain that we all feel after the latest mass shooting, and the confusion we all feel about the Russia probes. These stories have come together. While these grieving students in Parkland, Florida are asking politicians to protect them and announcing a march on Washington, the president of the United States is making it about himself. [...] It's clear the president is feeling the heat of Robert Mueller's special counsel, and he's lashing out, implying that the FBI might have failed to stop the shooting because it's too obsessed with Russia.