U.S. Representative Gabrielle Giffords of Arizona was shot in the head while holding a public event in Tucson, Fox News and National Public Radio reported on Saturday.
Fox said 11 other people were shot when an unidentified gunman ran up and began shooting indiscriminately as Giffords addressed supporters.
Giffords was shot point blank in the head, Fox said. The network said the gunman was in custody.
Giffords, 40, a Democrat, is married to U.S. astronaut Mark Kelly. She took office in January 2007, emphasizing issues such as immigration reform, embryonic stem-cell research, alternative energy sources and a higher minimum wage.