What does the Trump Tower meeting testimony tell us about the Mueller investigation?

Thousands of pages of testimony from key figures who were at that Trump Tower meeting in June 2016 were released today by the Senate Judiciary Committee, shedding some new light on the players involved and the fallout once news of the meeting went public. NBC News Intelligence and National Security Reporter Ken Dilanian and former Federal Prosecutor Sam Buell join Andrea Mitchell to discuss what is in these documents, and what it could mean for the Russia investigation.