Bring a plastic whistle. Even a small one. Keep it in your bag or purse or pocket or on your keychain.
That way, if you see anything that looks wrong anywhere at the rally, you - and everyone around you - can stand up and start blowing those whistles and pointing.
If the people in Butler PA could have done this when they saw the kid on the roof with the gun, things might have been very different. (Don't get me wrong - they tried. But just yelling is not enough when a huge rally is going on.)
Yes, the rally regulations say you cannot bring whistles and noisemakers. That means you're not to use them during a "normal" rally, which is understandable.
I'm talking about keeping something with you in case of emergency. That's very different.
My grandfather taught me how to do the two handed whistle when I was young. It’s surprised people many times over the years and I’ve had a great time with it. Ha. Also been useful to keep family together in crowds. It took me a good while and some diligence to learn. But he and I were very pleased with ourselves when I mastered it. 😆