He had no apparent motive. This story was probably chosen for the front page of the national newspaper because shocking and inexplicable crime stories have mass entertainment appeal as real-life crime shows.
I imagine a typical reader for the Houston Chronicle as someone who wishes to be generally well informed about issues that affect their life. A reader of the Houston Chronicle may use the paper as a compliment to other news outlets such as evening news programs. I imagine the readers of the Houston Chronicle as including more local businessmen than the national paper.
A reader of USA Today may wish to avoid being entirely uninformed about the news, and may have a limited amount of time to keep up with the news. The USA Today is short enough to be read and skimmed through in a short period of time. It had ten pages of news compared to Houston Chronicle's fourteen. I think the USA Today readers may be slightly younger, and may not have the patience for in depth