Not suspicious at all.
Via Rise News:
A six-car commuter train with 50 passengers left a station without the operator on board. The train traveled through four other stations without stopping. This frightening incident happened in Braintree, Massachusetts.
Kgun9.com reports on how the train was stopped: “MBTA operations disabled the train and brought it to a stop by cutting off power to the electrified third rail”.
It is being reported that the train was tampered with. “This train was tampered with, and it was tampered with by someone who knows what he was doing,” Governor Charlie Baker said, according to the Boston Globe.