walkouts in dallas where students formed an impromptu mariachi band. tens of thousands send a message that america is a nation of immigrants. >> what a story. thanks to nbc's scotty schwartz for that report. still ahead, is snap chat worth as much as they think it is. now the arrest of the company's chief. we'll have the latest on what's been a difficult year for samsung when we look back in a moment. ♪(music plays)