The manifesto he composed before his murderous rampage was just released; you can read the whole thing here [pdf file], and it's worth reading in its entirety for a number of reasons. But I especially took note of Part III:This was a symbolic killing. Who I wanted to kill was every Democrat in the Senate & House, the 100 people in Bernard Goldberg's book. I'd like to kill everyone in the mainstream media. But I know those people were inaccessible to me. I couldn't get to the generals & high ranking officers of the Marxist movement so I went after the foot soldiers, the chickenshit liberals that vote in these traitorous people. Someone had to get the ball rolling. I volunteered. I hope others do the same. It's the only way we can rid America of this cancerous pestilence.
That seems to sum up Adkisson's thinking: He wanted to be the spark in a wave of similar fed-up-niks taking their anger out on liberals.
It's also worth looking at the kind of reasoning that led him there:
In a parallel train of thought; It saddens me to think back on all the bad things that Liberalism has done to this country. The worst problem America faces today is Liberalism. They have dumbed down education, they have defined deviancy down. Liberals have attack'd every major institution that made America great. From the Boy Scouts to the military; from education to Religion. The Major News outlets have become the propaganda arm of the Democrat Party. Liberals are evil, they embrace the tenets of Karl Marx, they're Marxist, socialist, communists.