As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EXPERIENCED NR 1 ENGINE VIBRATION, FOLLOWED BY A/C YAWING TO THE LEFT. N2 RED WARNING LIGHT ILLUMINATED. ENGINE THROTTLE WAS RETARDED TO IDLE, BUT VIBRATION CONTINUED. CREW PERFORMED ENGINE SHUT-DOWN PROCEDURES. AIRCRAFT RETURNED TO OAK AND MADE AN UNEVENTFUL LANDING. REPLACED ENGINE ASSEMBLY PER BOEING M/M.