Citigroup Center is a 42 story, 588-foot (180 m) skyscraper in Chicago, Illinois. It is located at 500 W. Madison (between Clinton and Canal Streets). The structure was designed by the architecture firm Murphy/Jahn in a late modernist style. The building was named the Northwestern Atrium Center. It was constructed between 1984 and 1987.
On 8 December 2006 a man opened fire in a law office located on the 38th floor of the Citigroup Center. Four people, including the gunman, were killed. One person survived.[1]