Tonight on The Last Word: Donald Trump uses the CNN town hall to spew lies and attack his rivals. Also, Trump contradicts his legal team on how classified documents ended up at Mar-a-Lago. Plus, Senate Democrats hold a gun safety meeting in wake of mass shootings. And Ukraine prepares for a counteroffensive against Russia. Mehdi Hasan, Charles Blow, Andrew Weissmann, Fred Guttenberg and Timothy Snyder join Lawrence O'Donnell.