Brigadier generals are nominated by the president and confirmed by the senate

U.S. law explicitly limits the total number of general officers who may be on active duty. The total number of active duty general officers is capped at 218 for the Army, 62 for the Marine Corps, 170 for the Air Force, and 21 for the Space Force.

All brigadier generals must retire after five years in grade or 30 years of service, whichever is later

If he’s a brigadier general then he’s one of the few and he’s gonna be an older dude