The National Transportation Safety Board has determined that the engineer of Amtrak Northeast Regional train no. 188 was likely distracted by radio traffic about an emergency situation on a Southeastern Pennsylvania Transportation Authority Regional Rail train and lost track of where he was moments before the May 2015 overspeed wreck at Frankford Curve that killed eight and injured 200.

Amtrak Engineer Brandon Bostian, who the NTSB described as a “qualified, experienced, and apparently alert engineer” in its May 17, 2016 report, had just passed a SEPTA train with a shattered windshield and was “very concerned” about its engineer, who had requested medical attention, NTSB said. That area in North Philadelphia on the Northeast Corridor is well-known as a trouble spot where heavy objects are sometimes thrown at or dropped into the path of trains. Bostian, distracted, likely “lost track of where he was” and didn’t realize he was seconds away from entering a 55-mph curve at 106 mph.

Bostian suffered a severe concussion. He told investigators his memories of the crash are foggy, though he does recall “holding onto the controls tightly and feeling like, OK, well this is it, I’ m going over,” NTSB member Robert Sumwalt said. ““He went, in a matter of seconds, from distraction to disaster.” According to the NTSB, amnesia after a severe blow to the head is possible.

Frankford Curve at the time was not equipped with an enforced speed code for eastbound trains, nor was ACSES, Amtrak’s version of PTC, activated there. Following the wreck, Amtrak installed speed codes on all non-equipped curves. By the end of 2015, ACSES had been activated on the entire NEC.