Ok so read the letter so let's go to the statue listed in the letter and possibly find a possible answer:
(h) The sheriff shall revoke any permit upon the occurrence of any event or condition subsequent to the issuance of the permit, or the applicant's subsequent inability to meet a requirement under this Article, which would have resulted in a denial of the application submitted to obtain the permit if the event, condition, or the applicant's current inability to meet a statutory requirement had existed at the time of the application and prior to the issuance of the permit. The following procedures apply to a revocation:
(1) The sheriff shall provide written notice to the permittee, pursuant to the provisions of G.S. 1A-1, Rule 4(j), that the permit is revoked upon the service of the notice. The notice shall provide the permittee with information on the process to appeal the revocation.
(2) Upon receipt of the written notice of revocation, the permittee shall surrender the permit to the sheriff. Any law enforcement officer serving the notice is authorized to take immediate possession of the permit from the permittee. If the notice is served by means other than by a law enforcement officer, the permittee shall surrender the permit to the sheriff no later than 48 hours after service of the notice.
(3) The sheriff shall insure that the list of permits which have been revoked is immediately updated so that any potential transferor calling to check the validity of the permit will be informed of the revocation.
(4) A permittee may appeal the revocation of a permit pursuant to this subsection by petitioning a district court judge of the district in which the permittee resides.
(5) Any person who willfully fails to surrender a permit upon notice of revocation shall be guilty of a Class 2 misdemeanor.
(i) A person or entity shall promptly disclose to the sheriff, upon presentation by the applicant or sheriff of an original or photocopied release form described in subdivision (5) of subsection (e1) of this section, any court orders concerning the mental health or capacity of the applicant who signed the release form. (1919, c. 197, s. 3; C.S., s. 5108; 1959, c. 1073, s. 2; 1969, c. 73; 1981 (Reg. Sess., 1982), c. 1395, s. 1; 1987, c. 518, s. 1; 1995, c. 487, s. 2; 2006-39, s. 1; 2006-264, s. 4; 2008-210, s. 3(a); 2009-570, s. 7; 2010-108, s. 4; 2011-2, s. 1; 2011-56, s. 2; 2011-183, s. 13; 2011-268, s. 10; 2013-369, s. 17.2(a); 2013-389, s. 2; 2014-115, s. 23.5(a); 2015-195, ss. 10(d), 11(c), (f), (j); 2016-77, s. 9(a).)
So to me it looks like they issued the permit possibly before getting the medical release back that you have to fill out and found something that disqualified the person once it came back. Seems like it must be a fairly common thing to have an entire sub section in the statute. So it seems like those issues were before his permit was issued.
Don't know this to be truth but it seems more plausible than the hospital just sending over random dudes medical records.