If you do a google search for wdcsun21 you will see that they (DOJ and other government agencies) seem to be hitting a lot of logfiles. A number of the sites are political or tax related, but some are just regular sites like a hat company in BC Canada. There is a lot of commentary on the subject such as "Want to see just how desperate the Bastards are?" and "Watching Big Brother Watch Us".
Have you created any reason why the DOJ would want to "keep an eye" on you? What is the image that they are looking at?
I wouldn't worry about it; DOJ does have a lot of employees and they'll be visiting from DOJ domain names. If you're in an illegal business then maybe you have something to think about, but I wouldn't go overboard on it otherwise. I see all kinds of govt domains, on one of our sites, going into the employment area.
I think it is a bot because once a day, it pulls the robots.txt and the first page and the image on the first page. It is a site about a government backed loan program. Maybe that has something to do with it. I am not worried, just curious.