The current thinking about Jared Loughner's motive -- such as it was -- is that he was affected by two currents in his life.
On the one hand, he was becoming more and more fixated on Rep. Gabrielle Giffords (D). He had met her, he had become interested in her, and he found himself disagreeing with her positions, as she became more successful and prominent.
On the other hand, he was experiencing setbacks as his life moved into a downward spiral. He was turned down by the military and asked to leave the community college, as he was apparently becoming increasingly more mentally troubled.
To the extent that he was reading extremist Web sites, investigators at this point believe that's not likely a major factor. However, they say they are still going through his computer and emails to learn more about that.