Last Updated Feb 1, 2016 5:15 PM EST
WASHINGTON - The last thing Amtrak engineer Brandon Bostian remembers before last May's fatal crash in Philadelphia is pushing the throttle forward to pick up speed and then braking when he felt the train going too fast into a sharp curve, according to a transcript of his interview with federal accident investigators.
When he realized the train was about to derail, Bostian recalled holding tightly to the controls and thinking, "Well, this is it, I'm going over."
The transcript was among more than 160 documents released Monday by the National Transportation Safety Board. The documents don't come to any conclusions on the cause of the crash but offer a glimpse into what investigators have learned thus far.
Bostian has already been cleared of using his cellphone during the crash.
NTSB investigators have said previously that the train accelerated to 106 miles per hour in the last minute before entering a curve where the speed limit is 50 mph. In the last few seconds the brakes were applied with maximum force, but the train was still traveling at over 100 mph when it left the tracks.
Congress had been pressing the safety board for answers to the key question of whether engineer Brandon Bostian was using his phone. Bostian suffered a head injury in the crash, and his attorney has said the engineer doesn't remember anything after the train pulled out of Philadelphia's 30th Street Station, the last stop before the derailment.
Among the most illuminating parts of the federal investigation are two transcripts of interviews Bostian had with investigators, one immediately after the May 12 crash that killed eight people and injured nearly 200 others, and the second in November.
The train's data recorder shows it reached a speed of 106 mph, then the emergency brake was activated and the speed dropped to 102 mph as it entered a sharp curve in Frankford Junction, one of the sharpest curves in Amtrak's northeast corridor.
By then it was too late, and the train derailed. The speed limit for the curve is 50 mph. The limit for the stretch of track prior to the curve is 70 mph, although there is a portion prior to that where it is 80 mph.
"Once I pushed the throttle forward in an attempt to bring the train up to 80 miles an hour, I don't have any other memories until after the train was already in the curve," Bostian said in the November interview.
Bostian suffered a possible concussion and had other minor injuries.
An NTSB official described Bostian as "extremely cooperative" with investigators. The official, who wasn't authorized to speak publicly, talked to reporters on condition of anonymity shortly before the board released the documents.
Lawyer Tom Kline represents several of the hundreds who were injured.
"The train was being operated at 106 miles per hour, and there was a system that could have been in place that was in fact on place going the other way on the tracks that could have prevented it," he told CBS News' Kris Van Cleave.
That technology, positive train control, or PTC, is now active along Amtrak's heavily used Northeast corridor linking Boston to Washington D.C. Amtrak's Chris Jagodzinki showed CBS News how PTC prevents a train from going too fast.
"Now what happens here is this -- traction blocked, putting on the brakes, taking away all my power in the locomotive and just giving me penalties, now it's applying the brakes," he explained. "I can't do anything, I can't do anything. The computer has taken over."
NTSB has wrapped up its investigative phase into the accident. Next, investigators will analyze the evidence, prepare a report on the probable cause of the derailment and make safety recommendations. A draft report is expected to be delivered to board members in a meeting not yet scheduled, but that will likely happen around the May 12 anniversary of the crash.
Bostian provided his cellphone to investigators, who say that there's no indication he was using it while operating the train.
Other avenues of investigation have also turned up dry holes, according to previous statements by investigators. The data recorder shows the train's top-of-the-line new Siemens engine was functioning normally. No anomalies were found in the tracks or signal boxes. There was no vehicle or object on the tracks.
The train's assistant conductor said that before the crash he heard Bostian on his radio say the train had been hit by something. Trains operating in the Northeast corridor are frequent targets of rock-throwing vandals. Other trains in the vicinity of Frankford Junction reported being hit by rocks that evening not long before the derailment. A small dent was found in the windshield of Amtrak 188's locomotive.
Bostian has been suspended without pay since the crash. A letter from Amtrak in the NTSB files shows he was suspended for speeding the night of the crash.