(AP) - Jared Lee Loughner agreed Tuesday to spend the rest of his life in prison, accepting that he went on a deadly shooting rampage at an Arizona political gathering and sparing the victims a lengthy, possibly traumatic death-penalty trial.

His plea came soon after a federal judge found that months of psychiatric treatment for schizophrenia made Loughner able to understand charges that he killed six people and wounded 13 others, including his intended target, then-Rep. Gabrielle Giffords.

"I plead guilty," the 23-year-old college dropout said.

His hair closely cropped, Loughner was not the smiling, bald-headed suspect captured in a mugshot soon after the January 2011 shooting.

Wearing khakis, Loughner sat quietly throughout the hearing and smiled at one point when a psychologist testifying about his competence remarked that he had bonded with one of the federal prison guards.

After the hearing, Loughner's parents cried and embraced. The victims mostly just watched without expression.

"He's a different person in his appearance and his affect than the first time I laid eyes on him," said Judge Larry A. Burns, who then accepted the plea agreement and added that he found it to be in the best interest of everyone involved.

The outcome was welcomed by some victims, including Giffords herself, as a way to move on.

"The pain and loss caused by the events of Jan. 8, 2011, are incalculable," Giffords said in a joint statement with her husband, Mark Kelly. "Avoiding a trial will allow us - and we hope the whole Southern Arizona community - to continue with our recovery."