Accused killer Jared Lee Loughner is prepared to plead guilty on Tuesday for the 2011 mass shooting in Tucson, Ariz., that left six people dead and critically wounded Rep. Gabrielle Giffords, according to the Los Angeles Times.

According to the paper, two sources familiar with the trial’s proceedings said mental health experts had determined Loughner was fit to stand trial, and that they would testify to that effect on Tuesday in U.S. District Court in Arizona. Some had speculated whether Loughner was criminally insane and should be institutionalized, not incarcerated, for allegedly carrying out the shooting.

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The Times said it was unclear whether Loughner would plead guilty to every charge against him, or only to some.

Loughner is charged with five federal counts, including the attempted assassination of Giffords. Prosecutors had indicated that they could pursue the death penalty, though it is unknown if that will come off the table as part of a plea deal.

Loughner is accused of opening fire on a Congress on Your Corner event in Tucson, Arizona in January 2011 in an attempt to murder Giffords. Though Giffords survived a shot to the head, six others died and 13 others were wounded in the attack before three bystanders subdued Loughner as he tried to reload his gun.

Giffords briefly returned to Congress after extensive physical therapy before stepping down earlier this year.