(Reuters) - A college dropout pleaded guilty on Tuesday to killing six people and wounding 13 others, including then-Representative Gabrielle Giffords, in a shooting rampage in Tucson, Arizona last year.

Jared Loughner, 23, pleaded guilty to 19 criminal counts, including murder. He entered his guilty pleas in federal court in Tucson shortly after he was ruled mentally competent to stand trial by District Judge Larry Burns.

Under a plea agreement, federal prosecutors, who originally charged Loughner with 49 criminal counts, have agreed not to seek the death penalty against him.

"I plead guilty," Loughner, dressed in a khaki prison jumpsuit, said to each of the 19 counts read in court by Burns.

The 19 counts include murder, attempted murder and the attempted assassination of Giffords.

Giffords, an Arizona Democrat who was seen as a rising star in the party, was meeting constituents at a Tucson supermarket in January 2011 when she was shot through the head at close range. The six people killed include a federal judge and a 9-year-old girl.

Mark Kelly, Giffords' husband, said in a statement released before the hearing that the couple had been in touch with federal prosecutors and were "satisfied" with the plea agreement.