Court documents filed Sunday in the US District Court in Phoenix suggest that the violent attack was a premeditated assassination attempt. Federal investigators executing a search warrant on Loughner’s home opened a safe and discovered an envelope with handwriting stating “I planned ahead,” and “My assassination,” and the name “Giffords,” according to court documents. The envelope includes what agents said appears to be Loughner’s signature.
FBI Director Robert Mueller, who flew to Arizona after the shooting, said at a news conference Sunday in Tucson before the federal charges were announced that Loughner was not cooperating with the investigation but is believed to have acted alone. It was premature to speculate on a motive, Mr. Mueller said, but it "appears that the target was the congresswoman.”
Investigators had sought a second man, described as a "person of interest," for questioning, but Sunday night the Tucson Sheriff's Department said the man had been cleared. The man, who was seen in video surveillance tapes, is a cab driver who reportedly told detectives that he drove Loughner to the strip mall at 9:59 a.m. and had briefly followed Loughner while he sought change to pay his fare. Detectives are satisfied with the explanation, the Sheriff's Department said.