Jared Loughner has pleaded guilty to killing six people and wounding 13 others at a shooting in Arizona.
The 23-year-old was ruled mentally competent to stand trial for 19 counts, including the attempted murder of former-congresswoman Gabrielle Giffords.
Giffords was meeting constituents in Tucson early last year when she was shot through the head at close range.
Those killed included a federal judge and a 9-year-old girl.
Under the plea agreement, federal prosecutors have agreed not to seek the death penalty.
SOUNDBITE: UNITED STATES ATTORNEY JOHN LEONARDO SAYING (English):
"The attorney general decided to allow the guilty plea to life without the possibility of parole in the hope that providing certainty to the resolution of this case at this early stage would avoid any delay or disruption in the ongoing healing process for the victims, the Tucson community and the nation."
Victims of the shooting welcomed the plea.
Loughner will be sentenced on November 15.
