>> it actually had an impact that they noticed on their seismographs there. >> the terrifying accident is caught on camera by an employee of the occupational safety and health administration, a federal agency set for working standards. patrick is on site that day for a visit. seconds before the collapse, his colleagues begin recording the crane, not for work but for pleasure. >> we were videoing it just to see and it turned out to be the best evidence we have. >> iron worker jeff kasinski is watching it from a bucket suspended from a crane inside the stadium. >> you don't go to work expecting, you know -- you don't expect to see one of the most catastrophic accidents we've