They may also have been some other Federal Law Enforcement Officers from something like the US Marshals. We've seen them detailed at some of the really big events. As this was a small event, my guess is they're from the local USSS office.
Hillary! has folks on her "team" whose job it is to intimidate - by whatever means. And you did right by checking out credentials yesterday.
Excellent FReep yesterday, firebrand! And two SATANS, too! I'll bet Hillary! was so angry at your presence that she was already seeing double. One of these book-signings soon... she's gonna have a meltdown. And the press will be there to see it. Whether they'll cover it is another thing entirely. But either way, FReepers here will know about it because FReepers will be there to see it realtime.