An eye witness reported that the truck hit the superstructure and knocked pieces from it. If the superstructure is not intact, the bridge deck has no support. They said that after some was knocked loose the rest of the superstructure buckled and folded.
I'm glad that it appears that all who went down with the bridge were rescued alive and are okay. I feel very sorry for the truck driver. If he's found to be responsible, his company must pay for the cost of the bridge repairs. I hope that they carry lots of insurance.