About 5 p.m., on August 17, 1984, after southbound Chicago Transit Authority eight-car "A" train No. 135 left the Montrose Avenue Station and as it slowly ascended a 3.1-percent grade, the motorman saw "yellow dynamic" brake lights illuminated on the second and seventh cars. The train rolled to a stop, and the motorman secured the cab and went back to cut out the brakes on the second car. While the motorman was out of the cab, train No. 135 began to roll backward down the grade. The motorman ran back to the cab and attempted to stop the train; however, he did not stop it. Train No. 135, moving at about 20 mph, struck Chicago Transit Authority eight-car "B" train No. 143, which was standing just south of the Montrose Avenue Station. One passenger was killed, and 46 passengers and 3 crewmembers were injured.