(CNN)One of three conductors aboard the Amtrak train that derailed in Philadelphia this week told investigators she heard the locomotive's engineer say the train had been struck by an object, National Transportation Safety Board member Robert Sumwalt said Friday.
The assistant conductor said she overheard radio transmissions made Tuesday by Amtrak engineer Brandon Bostian and the engineer of a Southeastern Pennsylvania Transportation Authority (SEPTA) train.
"She recalled that the SEPTA engineer had reported to the train dispatcher that he had either been hit by a rock or shot at, and the SEPTA engineer said that he had a broken windshield, and he placed his train into emergency stop," Sumwalt said. "She also believed that she heard (the Amtrak) engineer say something about his train being struck by something."
Bostian was interviewed Friday afternoon for the first time since the derailment of Amtrak Northeast Regional Train 188. Eight people were killed and more than 200 were injured.
While he was "extremely cooperative," he had "no recollection" of anything that happened once the train passed the North Philadelphia station, about 3 miles from the crash site, Sumwalt said. Bostian suffered a concussion, among other injuries.