Meet the man police say brought the world's biggest subway system to a screeching halt. 

Isaiah Thompson, 23, is suspected of pulling the emergency brakes on up to 40 trains in New York City, causing delays that cascaded through the subway system.

According to authorities, the alleged culprit used the same M.O. every time, climbing into the last car through the rear door. Somehow, Thompson allegedly had his own master key that he used to gain access to the train operator's cab, which is always empty.

Then, he would allegedly pull the emergency brake inside. When the train came to a halt, he jumped onto the tracks and made his escape. 

Police are investigating whether Thompson is responsible for delays over a four-month period, impacting 750 trains and an astonishing 1.3 million commuters. 

Thompson is what's known as a subway surfer, part of a sub-culture that rides on the outside of train cars, sometimes even on the roof. He went viral last year for riding outside a subway car for more than half a mile. 

Thompson faces charges of reckless endangerment and criminal trespass. He has not yet entered a plea. 

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