Who are the Oath Keepers, and what are they doing in Ferguson, MO?

I’ve seen news reports about the Oath Keepers showing up in Ferguson, MO on the anniversary of the shooting of Michael Brown. I’ve read some of their website (link above), their official blog, and it seems to me to be a “prepper” group, consisting of active and former military and law enforcement.

I wonder what they are hoping to accomplish by showing up in Ferguson, where tensions are already high, and where a lot of work has been done between the community and the police department.

Edit: I just heard a report that they were there in support of a journalist from Infowars, the website run by conspiracy theorist Alec Jones.