Giffords shooting investigation turning towards motive

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TUCSON, Ariz. -- Investigators are learning more about the suspect who shot 20 people, killing six and leaving Congresswoman Gabrielle Giffords in critical condition.

FBI director Robert Mueller says investigators are still trying to figure out why 22-year old Jared Loughner opened fire at an event for Congresswoman Gabrielle Giffords.

"The investigation is barely 24 hours old and it's a little bit early to speculate in those motives," said Muller.

Sheriff Clarence Dupnik revealed Loughner may have been in touch with the congresswoman back in 2007.

"There was some correspondence between Giffords' office and him about a similar event and he was invited to attend," Said Sheriff Dupnik.

A criminal complaint filed Sunday references the event. Documents show a safe seized from the Loughner home contains a letter Giffords sent to Loughner dated august 30, 2007.

The letter apparently thanks Loughner for attending the congress on your corner at the Tucson mall.

The complaint also mentions an envelope in the safe with the words written, "i planned ahead," and, "my assassination," and, "Giffords."

Investigators are also looking into Loughner's on-line activity, including videos posted on YouTube.

"Any activity he had whether it be email or other communications we'll be looking at every one of his associates to determine whether or not they continue to present a threat," said Dupnik.

Investigators also suggest Loughner went to the Safeway prepared to cause far more blood shed. The sheriff says Loughner brought a 9 millimeter Glock with at least two magazines. A female bystander stopped him from reloading his second clip.

"There would have been a huge greater catastrophe if had he been successful in doing that," said Dupnik.

Dupnik says the second magazine contained 31 rounds.

Investigators previously released a surveillance photo of a person of interest.  They say now the man in the photo is a cab driver who gave Loughner a ride, but he was not involved in the attack.

Loughner will have an initial appearance Monday in a federal court in Phoenix.