Apparently home schooled (high school years), didn't like gays or abortion and a self described conservative.
"The Austin American-Statesman newspaper reports that he was homeschooled by his mother during his high school years. His parent's home is now being searched by authorities, according to the newspaper.
"I officially graduated Mark from High School," his mother wrote on Facebook in a 2013 post showing her son.
"He's thinking of taking some time to figure out what he wants to do...maybe a [religious] mission trip," his mother wrote."
...
"US media have uncovered a 2012 blog which was written under the suspect's name and appeared to be for a university course that he attended.
In the blog called "Defining my Stance", he purportedly describes beliefs that "gay marriage should be illegal", opposition to abortion and why the sex offender registry should be eliminated.
In the blog, he defines himself as "a conservative".
"But I don't think I have enough information to defend my stance as well as it should be defended," he says, adding that he is taking the course "because I want to understand the US government, and I hope that it will help me clarify my stance".
http://www.bbc.com/news/world-us-canada-43490247