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The investigation: What we know so far
Over a thousand federal, state, and local investigators are gathered in Boston trying to figure out who is responsible for the marathon attack. Chris Hayes talks about the status of the investigation with Grant Fredericks and former ATF special agent-in-charge James Cavanaugh.
The inexplicable weirdness of Rick Scott04:31
Bad news for some blue state GOP governors05:30
Leaks from the Mike Brown investigation surface07:27
Amazing video of Ottawa post office evacuation01:35
Who was the Ottawa gunman?07:38
Shooting attack in Ottawa stuns Canada16:11