That's just Monday morning quarterbacking. What would they say? What exactly did they know at the time?
1. "You're being shot at"
2. They knew enough to run off the stage as fast as the could.
Any more questions?
Well... yes.
1) Who makes the announcement, and on what authority? I hope you aren't implying the band should? They probably had no idea... they had earpieces in, may not have even heard the shots and were just reacting to the roadies waving them offstage.
2) If it turns out they were wrong and people were injured in the stampede that would surely follow, is that person liable for creating a panic?
Dunno... if I were there and had control of the soundboard and a mic, I wouldn't have done anything. I guess you would have... you're better than me. Of course I probably had headphones on too so I could hear the mix, but hey, you be you.