I'd have to know more about his computer searches before making any decision as to whether it was murder or not.
I've been to the "childfree" forum of Reddit. I visit Reddit regularly and enjoy their parenting forum, which often has links to posts in the childfree forum; people cross posts things between the two all the time -- sometimes for information and sometimes for trolling. As a person who was decidedly childfree before becoming a parent overnight, I find both fora interesting.
I've also read articles on kids dying in hot cars. The Washington Post ran a great article about this a year or so ago. I think every parent I know read it. Some of them did some additional research.
Knowing he was an IT guy who still had this stuff on his computer makes me think two things: he was a normal parent and this was a terrible accident or that he thought he'd never be suspected and therefore didn't need to cover his tracks. Without knowing more, I have a reasonable doubt.