The couple and their two children simply disappeared from their home one day. They left their two dogs behind, and left dishes in the sink and a bowl of half-eaten popcorn , although the article doesn't mention those details. They did not take any money out of the bank and their empty car was found in a mall parking lot.
The only lead , their computer shows that they did some searches about passport requirements to travel into Mexico. There is also a border security camera photo showing two adults and two kids walking into Mexico through a border checkpoint, but it's impossible to identify the people in the photo.