Why were people lying about rescuers being in danger? Just trolls? I think we would have heard by now if there were pirates out there stealing rescue boats at gunpoint.
Not necessarily lying or trolling. Persons with a low anxiety threshold may post (and re-post) a single report or rumour, not realizing that they thereby create problems rather than assist.
This is probably a part of the answer. Many reports we heard sounded almost like recordings they were so similar. I found myself anticipating some of this dialog just based on previous dialogs. As I noted earlier, when someone tried to inform listeners that the dam failure probably applied to a different geographic area than the one for their channel it was quickly followed by a person repeating that the dam was about to fail, the Coast Guard was right there with him, etc. I decided that someone either had a narrative they wanted to follow or that they didn't realize they were not on the Houston channel any more.
The National Guard and Coast Guard are armed and did respond to rescuers being attacked. Not sure if they actually fired back in response, or only forced them to leave.
We saw many official groups - most of the swiftwater rescue teams from central Texas, the National Guard, local fire and police departments, organized volunteer groups including the Texas and Cajun Navies, and the Coast Guard. Of those groups the only ones we encountered who weren't obviously armed were the Coast Guard. They may have had their firearms in their vehicles but they weren't on display.
No one that we talked with fired a shot or was fired at. During the several days that we were down there none of us heard a shot even though at times we were supposedly in the neighborhood where boaters had been attacked. We did find some neighborhoods where civilian boats were not allowed - authorities had blocked access except to Coast Guard, Nat'l Guard or other official group boats. Several of these neighborhoods were along the bayous where a lot of expensive homes were built. It seems unlikely that anyone was going to shoot at a rescuer in those areas.