calculus changed >> reporter: after two months of anger and unrest on campus, an announcement as sudden as it was stunning. >> i'm resigning as president of the university of missouri system. >> reporter: hours later the chancellor announced he'll be stepping down at the end of the year. students say this semester has been plagued with incidents of racial harassment. >> a lot of racial tensions. i'm glad that something has been done. >> reporter: in september the black student body president said a group of white students shouted the n word at him. >> i'm walking down the street. someone screams the n word out at me again. >> reporter: other students reported a swastika left on a dorm wall. and the university's response was lacking, even infuriating, they said. they could hardly believe the