Help in Cove Point

I have a bluebird nest (second brood) that was attacked last night. I found the box open and nest on the ground with two eggs and the young ones gone. I put the nest back in the box but mom and dad have been frantically flying about the box and trying to feed the young that are no longer there. I am not sure if I did the right thing. Should I have left the box alone? Should I just clean out the box? I am not sure what to do. I am so distraught. Any suggestions would be most grateful…. thank you.