For Alex Pretti, there is already a video found where he kicks a police car's tail light loose during an earlier protest (while also carrying a gun to that event, too), so circumstances are stacking against him, unfortunately.
I'd say, simply don't bring a gun to a protest! As then police won't need to do split second decisions about whether you are using lethal force against them or not.
If cops are too pussy for their job they can quit anytime, nobody's stopping them. The public should not have to give up firearms just because cops piddle their pants ehile being armed armoured ten times as much.
That's a different case, how does it have anything to do with this.
The Alex Pretti shooting is what started this thread (way up).
Though back to filming, while it's legal to just film a cop, then it may not be while an operation is ongoing. If you film the operation in quiet then I guess it's up to debate whether that is interfering with police work. But the protesters were also whistling along with the officers, i.e, giving away that they're there, etc.
To me saying "simply don't bring a gun to a protest" is according to constitutional law the same as saying "just don't say politically inflammatory things around officers who might accidentally interpret it as a personal threat and beat you".