From News Target:

In Washington state, for example, people received $150 for every bump stock they turned over to state police. The program attracted a lot of people; violators could face thousands of dollars worth of fines and as many as ten years in prison.
Now, however, their names and other personal information are about to be revealed to the public. Someone has filed a Public Records Act request to obtain the names and addresses of the people who surrendered their bump stocks as part of the program.