Tucson, Arizona (CNN) -- The suspect in the weekend shooting at an Arizona political meet-and-greet is scheduled to make an initial appearance Monday before a federal magistrate. Jared Lee Loughner will appear in a Phoenix, Arizona, courtroom at 2 p.m. Monday (4 p.m. ET), prosecutors said. He is accused of opening fire outside a Tucson supermarket, where U.S. Rep. Gabrielle Giffords, D-Arizona, was meeting with constituents Saturday. Six people were killed and 14 others wounded in the shooting. Giffords remained in critical condition Sunday after being shot through the skull, while a federal judge, a congressional aide and a 9-year-old girl were among the dead.
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NEW: A law enforcement official says suspect's parents were cooperative when interviewed
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Jared Lee Loughner faces federal charges in slayings, isn't talking to investigators
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Federal public defender has been appointed to represent Loughner
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Court documents say "my assassination" and "I planned ahead" scrawled on envelope
Gabrielle Giffords
Giffords
"Also recovered in the safe was an envelope with handwriting on the envelope stating, 'I planned ahead,' and 'my assassination' and the name '@placeholder,' along with what appears to be Loughner's signature," the affidavit says.