Knowing that there was an element of PTSD in Mr. Wheeler's background, I would immediately consider a psychogenic fugue state. This can be brought about when a person is confronted by a trigger. They can wander, often to their own detriment, with no memory of where they've been. These can be people who often spend a lot of energy "keeping it together". That's why others are so often shocked as the behavior doesn't seem like the person they know--often a well-respected and successful person. This might sound like something from a TV show, but it does happen and has been recently getting more and more attention, as we learn more about the aftermath of PTSD.
I have a hard time believing, however, that this was the very first incident. The others might have been kept quiet or within the family but I would really be surprised if this was the first time.