I looked this morning. There are hundreds and hundreds of James Holmes listed, many don’t have location or use something other than a picture of themselves as a profile picture so it will be hard to go through. It might be near impossible to determine which one his is depending on his personal security settings.
Some people think they can hide their identity because they are on Facebook under a false name and with a fake picture. They forget that their set of friends can uniquely identify them.
Somebody is going to be searching for the facebook identities of his relatives, co-workers, and classmates and looking for commonality. Probably on LinkedIn and similar sites too.