Law enforcement officials believe Congresswoman Gabrielle Giffords was the intended target of an armed attack in Tucson.

Pima County Sheriff Clarence Dupnik said at a Saturday evening news conference that "I don't have information about whether she was the first person shot, but yes, I believe she was the target."

The sheriff said Giffords was shot once in the head, and 18 other people were shot. Six are dead.