Jared Lee Loughner, the alleged gunman in last year's mass shooting outside an Arizona supermarket in Tucson that killed six people and wounded then-U.S. Rep. Gabrielle Giffords, pleaded guilty Tuesday to 19 charges in exchange for the government not seeking the death penalty.

Under the plea deal, Loughner will be sentenced to life in prison with no eligibility for parole, federal prosecutors said. His sentencing is scheduled for November 15, prosecutors said.

In court, Loughner also waived his right to pursue an insanity defense.

"My name is Jared Lee Loughner," the defendant told the court when he held up his right hand under oath.

Loughner calmly told the court he understood his guilty plea. "Yes, that is correct," he said.

"I'm 23 years old," he told the court. "I attended college for five years at a community college."

Earlier Tuesday, Judge Larry Alan Burns found Loughner competent to stand trial in a federal court in Tucson.

"He's a different person in appearance and affect," the judge said about Loughner, who was present in the courtroom. "He's tracking today. He appears to assist his lawyers. Court's own observations are that there's no question he understands what's happening today."

Loughner had been facing more than 50 federal charges, and the remaining offenses will be dropped in exchange for the guilty pleas if Loughner is sentenced within the terms of the plea agreement, according to the written agreement filed in court.

Under the pleas, Loughner admitted guilt in the attempted assassination of Giffords and the murders of federal employees U.S. District Court Chief Judge John M. Roll, 63, and congressional aide Gabriel M. Zimmerman, 30, prosecutors said.

Loughner also pleaded guilty to the attempted murders of federal employees and congressional aides Ronald S. Barber, 65, and Pamela K. Simon, 63, prosecutors said.

Loughner also admitted causing the deaths of Christina-Taylor Green, age 9; Dorothy "Dot" J. Morris, 76; Phyllis C. Schneck, 79; and Dorwan C. Stoddard, 76, prosecutors said.

Loughner admitted injuring with a Glock pistol 10 persons participating at an activity provided by the U.S. government and creating a grave risk of death to 13 more persons, prosecutors said.

Prosecutors agreed to a plea deal -- and not to seek the death penalty -- after taking into account Loughner's history of mental illness and the views of victims and their families.

"It is my hope that this decision will allow the Tucson community, and the nation, to continue the healing process free of what would likely be extended trial and pre-trial proceedings that would not have a certain outcome," U.S. Attorney General Eric Holder said in a statement.

U.S. Attorney John S. Leonardo in Arizona added: "Given the defendant's history of significant mental illness, this plea agreement, which requires the defendant to spend the remainder of his natural life in prison, with no possibility of parole, is a just and appropriate resolution of this case."

Walking with a bit of a slouch, Loughner cast a sneer at the packed gallery when he entered the courtroom. During the guilty plea proceedings, the gallery was quiet, with some people sniffing and wiping away tears.

An order from the court indicating the planned change of pleas was released Monday.

Loughner earlier had pleaded not guilty to the charges against him, including murder and attempted murder.

The January 8, 2011, attack killed six people and wounded 13 others, including Giffords, who was holding a meet-and-greet event with constituents.

Giffords, who was shot in the head, stepped down from her position in Congress in January 2012 to focus on her recovery. Ron Barber, an aide also wounded in the attack, now holds the seat.

Giffords' husband, Mark Kelly, said in a statement Tuesday that he and his wife are satisfied with the agreement.

"The pain and loss caused by the events of January 8, 2011 are incalculable," Kelly said. "Avoiding a trial will allow us -- and we hope the whole Southern Arizona community -- to continue with our recovery and move forward with our lives."

Susan Hileman, 58, who was wounded, said after the court proceedings that she was proud to be an American.

"This is the system doing its best. It's not a perfect solution," Hileman told reporters. "This is the best that can be expected."