Yeah, I'm sure that's it. Couldn't be that he was just some crazy bastard.
That would qualify him as having written some of them.
If this was not an extreme example of anti-Christian bigotry I would be tempted to agree with you. However, the verbal hatred I have encountered on Leftist and Libertarian websites make me question whether the acceptability of anti-Christian bigotry cannot, under the proper circumstances lead to the targeting and murder of Christians.
As an example, we can refer you back to the 1930s when anti-Semitism was perfectly acceptable not just in Germany but also in the rest of the world. The acceptance by a large number of people that it is OK to look at people of a certain race or creed as lesser is the first step. That can then lead to those who are emotionally ready to commit mayhem to do so, as long as the victim is of the despised class.
For some reason, the killer found affirmation that Christians were acceptable targets of his rage. Where could he have learned that?
Could it be he was a Christianphobe?