FBI found a 2007 letter from Giffords to the suspect

You asked me for the source of my claim.  My source is the Washington Post.

"Two law enforcement sources said that FBI agents had found a 2007 letter from Rep. Gabrielle Giffords (D-Ariz.) to the shooting suspect, with the words "Die, bitch" and "Die, cops" scrawled on it. The letter, which thanked [Jared] Loughner for attending an event of hers, was found in a safe in his Tuscon home, the sources said.

In 2007, there was no Tea Party movement and Sarah Palin was the obscure, recently elected governor of Alaska. If anything, the overhead heated political rhetoric at the time was coming from the left and was directed largely at President George W. Bush. It is time for all those whose reflexive reaction was to capitalize on this tragedy by blaming their political opponents (eg. the New York Times editorial page, the Daily Kos and Paul Krugman) to start issuing some apologies. They can start with Sarah Palin." (SOURCE)