Quoted from another forum:
DC9 had a right hydraulic system failure in flight. Plane landed without trouble using left hydraulic system. After landing pilot called for tow, but then elected to taxi to gate. During Taxi Capt shut down left engine. Big mistake.
Shutting down the left engine shut down the left hydraulic system. Now both the right and left hydraulic systems were inop. When the Capt realized he had no steering and brakes, he tried to stop the aircraft using the right engine thrust reverser. Well as every DC9 pilot knows (or should know), the right thrust reverser is powered by the hydraulic system. As the pilot panicked, he continued to pull more thrust reverse on the right throttle. The engine output increased but the thrust reverser was not deployed. The aircraft developed 90% forward thrust pushing it off to the left and into the parked A320. Maintenance personnel had to cut the pilot out as the upper cockpit was pushed down. Jet fuel everywear in the cockpit.