Tragedy in Minnesota When Bridge Collapses

At least four people were killed and 80 were injured in last night's rush-hour disaster when Minnesota's I-35W Bridge collapsed over the Mississippi River. Rescue workers say 20 to 30 more were pinned or trapped in the wreckage of falling steel, concrete and cars. In 2001, a report to the State of Minnesota said that while the bridge had not experienced "fatigue cracking," it did have poor "fatigue details" on the "floor truss system," described as the "primary load-carrying members" of the bridge's superstructure. Today, Mark Rosenker, head of the National Transportation Safety Board, said it will take time to figure out what went wrong. We get an update from the scene of an accident that could be a wake-up call about America's infrastructure.