As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB OUT FROM FIREFIGHTING DROP, THE CREW NOTICED A REAR OIL SYSTEM CHIP LIGHT ON THE RT RADIAL ENGINE. THE ENGINE WAS SHUTDOWN AND SECURED AND A IFE DECLARED. THE AIRCRAFT RETURNED TO BASE WITH AN UNEVENTFUL LANDING. UPON EXAMINING THE CHIP DETECTOR AND INSPECTING THE OIL FILTER SCREENS, NO METAL CONTAMINATION WAS FOUND.