A portion of the Skagit River Bridge, located in Mount Vernon, Washington catastrophically collapsed into the water below after a semi hauling an oversized load clipped a cross beam in 2013.  Luckily and amazingly, no one was killed by the incident, but 3 people were taken to the hospital for minor injuries as several cars fell into the river.  It took over 3 years to determine a cause and the report states that there were several causes.  First, below is security camera footage of the collapse, uploaded to Youtube by newschannel500, in which you can see just how quickly the collapse happened.