Demonstrators marched, stopped traffic and in some cases lashed out violently at police as protests erupted in dozens of U.S. cities following the killing of George Floyd after a white officer pressed a knee into his neck while taking him into custody in Minnesota. In Phoenix, Denver, Las Vegas, Los Angeles and beyond, thousands of protesters carried signs that said: He said I cant breathe. This is not in the spirit of Martin Luther King Jr.You are disgracing our city, she told protesters. You are disgracing the life of George Floyd and every other person who has been killed in this country. This is the only way were going to be heard.In Houston, where George Floyd grew up, several thousand people rallied in front of City Hall.