This from Dan McInerney:
United Airlines (B772, N782UA, ORD-NRT) 1/7/20This UA 772 made it to northern WI before turning around to come back with engine trouble. The Chicago Fire Department responded with a full ARFF assignment and escorted the plane back to the gate. As the plane turns you can see they had to shut the #2 engine down as evidenced by the lack of exhaust blur. Seen in the pictures is only a small part of the ARFF response; the Chicago Fire Department has the largest contingent of staffed ARFF vehicles and personnel of any airport in the world.

Dan McInerney photo

Dan McInerney photo

Dan McInerney photo

Dan McInerney photo