Did shooter plan Giffords attack for years?

Well, this would pretty much clear Sarah Palin, wouldn't it? Wall Street Journal reports:

After the shooting, investigators searched a safe connected to the shooting suspect, Jared Lee Loughner, and found a letter apparently sent to him by Ms. Giffords's office thanking him for previously attending a similar "Congress on your corner" event in 2007.

Much remains unknown about what motivated Mr. Loughner, who is in custody. But the initial evidence, including the constituent letter, has led law enforcement officials to think that the suspect had been thinking about the congresswoman for years, according to people familiar with the case.

Investigators also found paper on which the suspect apparently wrote the word "assassination" and "I planned ahead." The meaning or significance of that writing isn't clear.

UPDATE: 
  The charges against Loughner specifically state that Judge Roll was there to talk to Giffords about the burden on judges with regard to the immigration problem. Sheriff Dupnik jumped to a different conclusion, which was incomplete, biased or false in addition to yesterday's baseless assertion that right wing talk radio was responsible for the murders. 
  Initially Sheriff Dupnik blew off the reason for Roll being there, claiming that Roll just dropped in to visit his old friend Giffords. The sheriff, a law enforcement officer, didn't know, no basis for his claims, yet he made the claims anyway that.
  He's also the political animal who announced he would not enforce the new Arizona immigration law, if it were passed.
 What kind of a law enforcement officer does this?
  Kwame? Or Mayor Coleman?