Brandon Bostian's train was going 106 mph — more than double the speed limit on the tracks — on an S-curve when he slammed on the brakes in Frankford Junction in May 2015.
The train, headed to Washington D.C. from New York City, jumped the tracks, killing eight people and sending 185 to the hospital.
Federal officials said Bostian lost "situational awareness" and briefly thought he was past the S-curve and on a straightaway.
Bostian's lawyer during the trial described him as a longtime "train buff" with a perfect work record until that night, when he became distracted by people throwing rocks in the area, CBS News reports.
After a nearly 90-minute deliberation on Friday, March 4, Bostian was found not guilty of involuntary manslaughter and additional charges.
Amtrak settled for $265 million and later installed new technology that can automatically slow or stop a speeding train on its route from Boston to Washington.
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