To wit, 18 U.S.C. 875(d) "Interstate communications" provides in part
Read the whole thing here.
Whoever, with intent to extort from any person, firm, association, or corporation, any money or other thing of value, transmits in interstate or foreign commerce any communication containing any threat to injure the property or reputation of the addressee or of another or the reputation of a deceased person or any threat to accuse the addressee or any other person of a crime, shall be fined under this title or imprisoned not more than two years, or both.
Since the threat was made over email and probably crossed state lines there's probably a federal wire fraud charge for an eager prosecutor to dig up as well.
Hint: People who work in private equity are generally pretty smart, comfortable with conflict, have access to lawyers, and are very good at researching things. All in all, probably not a good group to try to blackmail.
Thanks for the chuckle, EP. I always love a good slapdown.