Unless you have some measurable damages, such as lost wages, physical injury, no lawyer would take on such kind of cases. If you have, then emotional distress would be attached on.
You can, however, get a restraining order to enjoin the person from doing that again. A restraining order is very hard to get so that you must prepare to show to the judge, specifically, what happened and who did that.
In lieu of restraining order, you can also sue the person yourself under theories of, (1) Defamation, and (2) public disclosure of invasion of privacy. Please understand that these are valid legal theories but unless you have physical injuries a lawyer would not help you, just for reputational damage or emotional distress, unless you want to pay him/her by hour. In civil lawsuit, you need to prove by preponderance of evidence.
Third option is to talk to the FBI field office or US district attorney's office because using internet to harrass, threaten, and annoy is a federal crime.