Mountain Men
The Mountain Men are a right-wing militia organization. They believe that the American government has become decadent and depraved, catering to the special interests of minority groups, bowing to the demands of political correctness, and willing to sell out the citizens to any corporation for enough political contributions. Their response is to train themselves to be independent of the government; they train extensively in survival skills and armed combat; they do not pay taxes or other wise interact with the government (which has them perennially at odds with law enforcement); and they protect their homes as sovereign territory. As part of their struggle, they have made contacts with a number of other organizations, including white supremacists (all members of the Mountain Men are white) and weapons smugglers, which is how they have come to lay a part in the bombing of the Super Bowl.
In the first mission, they stage a raid on television station to declare their independence and demand the release of certain members of the group jailed on tax evasion charges; this also serves s a cover for the stealing of a news van that is used to smuggle the nuclear bomb into the Super Bowl parking lot. In the second mission, a follow-up raid on one of the Mountain Men's compounds (in West Virginia) goes awry, and the HRT team is called in to rescue captured FBI agents who are being held hostage.
The Mountain Men, as the name may suggest, are outdoorsmen, and thus they tend to dress in a melange of hunting gear, army surplus camouflage, blue jeans, and boots. Their equipment is either off-the-rack hunting gear (hunting rifles, for example), available at gun shows (high-caliber handguns, for example), or smuggled heavier firepower weapons (AK-47 assault rifles). They wear very light or no body armor.
The Mountain Men are a motley group of individuals and have no unique leader character.