Checking various MN Statutes, Aaron would be hard-pressed to seek criminal charges for the dissemination of the letter. It's not a 626A.02 violation due to its original communication form being non-electronic. Its not criminal Invasion of Privacy, as that more focuses on Peeping Toms.
The best Aaron has in this specific instance is forms of common law invasion of privacy tort recognized by Minnesota courts.
Intrusion upon Seclusion:
This occurs when someone intentionally intrudes, physically or otherwise, upon the solitude or private affairs of another, and the intrusion would be highly offensive to a reasonable person. Photographing and disseminating a private letter without consent could qualify as an intrusion if the letter contained sensitive, non-public information. This is probably Aaron's best shot.
Publication of Private Facts:
This tort is committed when someone publicly discloses private facts about another person, the disclosure would be highly offensive to a reasonable person, and the information is not of legitimate public concern. Publishing a private letter online-especially if it contains intimate or sensitive details-can meet these criteria. Nick would likely chimp out with this one and countersue.
Appropriation of Name or Likeness:
This applies if Nick used April’s or Aaron’s name or likeness for his own benefit, such as for commercial purposes. Nick claims the letter was directly from Aaron, not the "AI" bullshit he spins with Supertips.gg. This is Aaron's personal property being used to sell Hackamania tickets. Nick would probably pretend a Newsworthiness Defense or De Minimis Use, claiming the letter wasn't the center stage selling point of the convention.
It's probable Aaron is going for a standard restraining order, but its worth checking out the civil liability possibilities.
It'll be interesting to see what Aaron's lawyer makes of the idea Nick thought he had permission to copy the original document and disseminate it uncontrollably.
I think it's as easy as advising NR's PO of the three threat(ish) tweets.
This is an interesting idea I overlooked,