Cliven Bundy is still grazing his cattle on that BLM land to this day.
The most likely situation is that he actually voluntarily told them that he has a firearm because he is a lawful gun owner with a concealed carry permit. Most gun owners know that this is the best way to interact with law-enforcement, for example, when you get pulled over. But we will not know because these agents do not wear body cams on purpose.
People have differing opinions, however the opinion most persuasive to me is you only tell them if asked unless the law requires otherwise. Volunteering you have a gun when there is no requirement to do so in my opinion adds unnecessary tension to the situation. IDK about in Minnesota, but in my state there is no duty to inform the police and you can basically only downsides to doing so, since they will be asking before you get into any situation where they're going to be going into your waistband to find out.
In one of the states I lived in, IIRC they changed the law to remove duty to inform because their cops had a history of executing people that informed them.
To me, this looks very much like testing the waters. Stephen Miller said, "To all ICE officers, you have federal immunity." ICE has blocked state law enforcement from investigations into the killings. ICE has said they're done with their investigation of the last one, and those fuckers are still working.
Aside from scale, what's the difference?
[EDIT:15-minute chunk of] video that lays out the evidence. https://www.youtube.com/watch?v=rThhm1-g1a8