Looking at the size of that terrace, I would think it could hold 2 people comfortably/safely. Were all 13 people on it or were some of the injured on the ground or on the terrace(s) below?
I never get on a crowded balcony for this very reason.
For some reason, I'm betting that large quantities of adult beverages were involved . . . which tend to impair rational thinking.
Now why do you suppose I would get that idea?