You mentioning the "pre cellphone"days is significant. What I said before was probably much more important when someone in the crowd would have to go off and find a phone. Today, everyone has a phone with them, and the instructions should probably be, "STOP FILMING!.....CALL 911!".You are correct. I was highly trained in first aid in the police, we covered giving instructions to others as you say, and told them ring and ambulance/ firetruck etc then come back and tell me it is done, as this was before cell phones it was imperative we knew it had been done, and generally it worked well, in both involving people and keeping them out of there way, it is a good way to ensure every is done