the wave of gun violence. the breaking news about mikhail gorbachev, the consequential world leader who took down the iron curtain. mr. gorbachev, tear down this wall. o donnell: as demand for new homes remains high, there is a labor shortage to build them. cbs s nancy chen on the women filling the void. this is the cbs evening news with norah o donnell, reporting from the nation s capital. o donnell: good evening to our viewers in the west and thank you for joining us on this tuesday night. a humanitarian crisis is unfolding here in america, as a state of emergency is declared in jackson, mississippi. the governor warning the capital s nearly 200,000 residents to not drink the water. the national guard has been called in to help get bottled water to those in need. and, it s not just drinking water. low-water pressure means people are unable to shower or flush their toilets. the problems at the water treatment plant came after days of heavy rains, resulted in a swolle