>> the post office is losing billions of dollars. it delivers packages for amazon at a very below cost. >> when "all in" starts right now. >> and good evening from new york. i'm chris hayes. 93 days ago, a former students of marjorie stoneman douglas high school armed with an assault rifle fatally shot 17 people at that high school in parkland, florida. with chants enough is enough and not one more than never again movement was born in the wake of that mass murderer created by grieving high school students determined to bring about change but awary enough to know it would probably happen again. today it happened again. a third fatal school shooting since parkland and the worst at santa fe high school in santa fe texas, outside houston. nine students and one teacher were shot and killed this morning, ten more injured. the suspect a 17-year-old student is in police custody. it was just one month ago that students at santa fe high school