Due to a technicality, the sea train is responsible for becoming a cyborg. When boarded Tom onto the sea train, Franky (then Cutty Flam) became enraged and tried to stop it. He did a full-on tackle to try to stop the train. When it ran him over, Franky's injuries were so severe that he had to replace his broken and damaged body parts with steel scrap.
The train reportedly did not have Positive Train Control, a safety system which could have prevented the crash by automatically slowing the train. Still, officials cautioned anybody from rushing to judgment and encouraged people to let the investigative process play out before jumping to conclusions.