This is similar to another incident where they came to a woman’s home and it was also captured on video. In both incidents they refused to show FBI identification and merely claimed to be “with” the FBI not agents. Matt Bracken has speculated they may be private contractors hired by the FBI.
Probably not FBI but DHS agents. They are involved in nebulous “criminal” investigations and looking for informants, so this looks more like their MO.
That's my take. It's cheaper to hire more of them when all one needs is to check for political leanings in conversation. They're FROM the FBI; they're not FBI agents.