Final answer:
Only law enforcement agencies are authorized to enter information about lost or stolen firearms into the NCIC database. Firearm owners, gun stores, and private investigators must report incidents to law enforcement, who will then handle the data entry.
Step-by-step explanation:
The National Crime Information Center (NCIC) is a centralized database that law enforcement agencies use for tracking crime-related information, including lost or stolen firearms. The only entities authorized to enter information about lost or stolen firearms into NCIC are law enforcement agencies. Firearm owners, gun stores, and private investigators do not have direct access to input data into NCIC; however, they would report such incidences to law enforcement, who would then take the responsibility to enter the relevant data into the system.