You can read a pretty good blow by blow here. In short, in an act of political retribution, a few of Christie's folks arranged for an access ramp to the George Washington Bridge to be "closed" for four days. Just boom. Closed. Street traffic backed up for miles. People sat in their cars until they ran out of gas. Ambulances couldn't get through and it appears one woman died as an indirect result.
It is a big deal. Jersey isn't a gentle state. Politics there are rough and tumble. I suspect that Mr. Christie is going to find out how rough and tumble they can get because if, and I say if, he knew about all this and it wasn't just some idiotic gotcha' plan hatched by his senior staff, someone soon is going to be asked the fatal question, "Are you going to lie to protect him and go to jail or are you going to tell the truth".