Understanding crowd dynamics can prevent disaster at cultural or sports events. Physicists investigating a recent crowd disaster in Germany found that one of the key causes was that at some point the crowd dynamics turned turbulent, akin to behavior found in unstable fluid flows. Never before have crowd disasters been studied by relying on a qualitative analysis of large public data sets. These include media and public authority reports, YouTube videos, Google Earth maps, 360Úphotographs, and other Internet sources.