(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. 
 
 The locomotive's windshield was shattered in the derailment. But Sumwalt said there is "particular damage" to the lower portion of the windshield that the FBI will examine. He described it as a "circular pattern that emanates out just a bit." 
 
 "We're very interested in this report. We want to learn more about it so we will use all sources of information that we can to independently validate that," Sumwalt said. 
 
 That includes meeting with the engineer of the SEPTA train. 
 
 NTSB Has secured outward-facing video from the SEPTA train in question and will be reviewing radio transmissions. #Amtrak — NTSB (@NTSB) May 15, 2015 
 
 Engineer reported no problems 
 
 Investigators are considering all possibilities, including speed, track conditions and human error, as they try to figure out what happened. 
 
 Much of the focus has been on Bostian, the 32-year-old at the controls of the train when it accelerated into a 50-mph curve at a speed of 106 mph. 
 
 JUST WATCHED Train accelerated from 70 mph to more than 100 mph Replay More Videos ... MUST WATCH Train accelerated from 70 mph to more than 100 mph 02:31 
 
 Bostian told investigators he was not ill or tired, felt "fully qualified and ... reported no problems with his train handling," Sumwalt said. 
 
 Under questioning, "he demonstrated very good working knowledge of the territory" where the derailment occurred, including speed limits at various points along the route between Washington and New York, which he made five days a week. 
 
 The NTSB will reassemble the train to connect its brake lines and test the braking system. 
 
 Other trains reportedly struck by objects 
 
 Former Transportation Secretary Ray LaHood said if the report of a projectile striking the train is true, "it would be a tremendous distraction" to the engineer. 
 
 Passenger Alfred Price told CNN he was sitting only three or four rows away from the engineer booth of the affected SEPTA train at about 9:10 p.m. Tuesday when he heard a loud boom and the train came to a stop. The engineer, who appeared shaken up, told passengers that something had hit the train. 
 
 I am aboard septa train to Trenton. Train was hit by something and came to a stop. Moments later the Amtrak train that derailed passed us. — Alfred Price (@TheAlfredPrice) May 13, 2015 
 
 Scott Knowles, another passenger on the SEPTA train, said the incident happened somewhere between Philadelphia's 30th Street station and the North Philadelphia station. The 30th Street station is the last stop the derailed Amtrak 188 train made before the crash. 
 
 Adding to the mystery of what happened the night of the derailment, passengers aboard a third train also reported their train getting struck by an object. 
 
 JUST WATCHED Passenger says earlier train struck by object Replay More Videos ... MUST WATCH Passenger says earlier train struck by object 02:48 
 
 Passenger Madison Calvert was aboard an Amtrak Acela train from New York to Philadelphia when he heard a "loud thud" that left part of the window next to him cracked in a circular pattern. 
 
 The incident happened right outside 30th Street station roughly 20 minutes before the crash, Calvert told CNN. 
 
 Philadelphia Mayor Michael Nutter said Wednesday that the Acela incident was not related to the derailment. 
 
 SEPTA engineers have reported "from time to time" projectiles hitting trains in this area before, said spokeswoman Kristin Geiger. 
 
 Co-workers describe engineer as 'very professional' 
 
 Bostian has had a reputation as a transportation buff since high school when he wrote about rail travel for his school newspaper. One of the online posts linked to him suggests he was working on a short-line railroad when he was 20 or 21. 
 
 What we know about the engineer 
 
 His LinkedIn profile says he joined Amtrak as a conductor after graduating from the University of Missouri in 2006. He became an engineer about 4½ years later. 
 
 His attorney, Robert Goggin, has said Bostian wasn't drunk, drugged or distracted by his cell phone Tuesday night. Nor has he had mishaps or major issues on the job, Goggin said. 
 
 The conductors aboard the train described to NTSB investigators a good working relationship with the engineer, calling him "very professional" and "great to work with," according to Sumwalt. 
 
 "He was very thorough always when it came to work (and) he was on point," said friend Xavier Bishop, who lost his job with Amtrak due to absenteeism issues. "He knew what he needed to know and if he wasn't sure about it ... he was going to call and make sure that he got the proper information." 
 
 Still, the engineer's seemingly stellar past hasn't stopped people from pointing fingers at him -- starting with Mayor Nutter. 
 
 JUST WATCHED Mayor: 'Clearly he was reckless and irresponsible' Replay More Videos ... MUST WATCH Mayor: 'Clearly he was reckless and irresponsible' 07:18 
 
 Nutter called Bostian's driving "clearly ... reckless," telling CNN, "There's no way in the world he should have been going that fast into the curve." 
 
 Investigators looking at speed as factor 
 
 CNN's Dr. Sanjay Gupta said the crash could have caused post-traumatic amnesia in which a person forgets parts of what happened before and after an injury. 
 
 Bishop, who "went up and down those rails with Brandon hundreds of times," is among those befuddled by the crash, saying, "I really believe something happened to prior to him getting to that curve. We all know what the speed limits are; it's not a mystery us." 
 
 The Philadelphia District Attorney's office is closely monitoring the investigation of the crash, but at this point there is nothing conclusive indicating Bostian was criminally reckless, according to an official with the DA's office. 
 
 One area of interest is whether the engineer could have possibly been distracted, perhaps by his cell phone. While Bostian's attorney said in an interview with ABC earlier this week that his client's cell phone was off at the time of the crash, investigators are pulling the engineer's phone records to determine whether there was any activity at the time of the derailment, according to a Philadelphia police official. 
 
 Bostian touted safety tools to override human error 
 
 Long before the derailment, Bostian apparently was an online advocate to prevent such a calamity -- technology to slow a dangerously fast train when an engineer does not. 
 
 "They have had nearly a hundred years of opportunity to implement SOME sort of system to mitigate human error," one post read. "But with a few notable exceptions (the rail industry) has failed to do so." 
 
 This message was one of several in recent years appearing to be written by Bostian on TrainOrders.com, which describes itself as a "railfan site" with photos, multimedia, chat and discussion forums. In one of the posts with the same "author" name, he writes out his name in full; in another, he uses his first initial. In one more, he describes himself as a student in Missouri originally from Memphis, Tennessee, which was true at the time. 
 
 Sumwalt has said already that there would have been no derailment if technology known as positive train control had been in place on the fateful override track to overrule an errant, oblivious or incapacitated engineer. 
 
 How does positive train control work? 
 
 Sumwalt has been seconded by rail experts, insiders and aficionados. Bostian himself apparently was an advocate of such an approach before the crash. 
 
 A 2011 post mentions how the NTSB decades ago put positive train control on its "most wanted" list of rail upgrades, then lamented that it took Congress to pass a law mandating the change by the end of 2015. Bostian apparently wrote that railroads have had many tools available for decades to curb crashes such as the one in Southern California involving a freight train and a Metrolink commuter train that killed 25 people in 2008. 
 
 "It shouldn't take an act of Congress to get (the rail) industry to adopt common-sense safety systems on their own," one message states. 
 
 Debate over Amtrak technology, funding 
 
 Many concur it is a shame positive train control wasn't installed already in places such as Frankford Junction, the curve in the track where this week's train crash happened. That includes Amtrak CEO Joseph Boardman. 
 
 "Had it been installed, it would have been prevented this accident," the Amtrak chief told CNN's Rene Marsh. "That's what I've been saying for a long period of time." 
 
 JUST WATCHED Amtrak CEO: Derailment could have been prevented Replay More Videos ... MUST WATCH Amtrak CEO: Derailment could have been prevented 01:43 
 
 And it's going to happen, at least, on Amtrak's busy Northeast Corridor -- which includes rails around Philadelphia -- by December 31, Boardman pledged. 
 
 Even after then, questions remain about why it's taken so long and what other infrastructure or technological improvements aren't happening. 
 
 Boardman said Amtrak and other transportation infrastructure nationally are significantly underfunded. This problem leaves agencies with tough questions about which safety upgrades to implement and which ones not to, with potentially dangerous implications. 
 
 There's no guarantee that more funding is coming. 
 
 On Wednesday, the Republican-led House Appropriations Committee voted to reduce grants to Amtrak by $252 million, a drop of about 15% from last year's level. 
 
 The move doesn't mean such a cut will become reality. But it certainly doesn't bode well for those -- such as Boardman and President Barack Obama -- who have called for more spending to repair decaying infrastructure in the wake of the latest crash. ||||| The intersection of Wheatsheaf and Frankford Ave. on May 13, 2015. ( ALEJANDRO A. ALVAREZ / Staff Photographer ) 
 
 Right before the fatal derailment of Amtrak Train 188 a conductor said she believes she heard the engineer say that a window on the train had been "struck by something," National Transporation Safety Board member Robert Sumwalt said Friday. In the agency's final briefing in Philadelphia on Tuesday night's horrific accident, Sumwalt said the FBI now was involved in the investigation of the crash that killed eight people and injured 200. The FBI confirmed that it is investigating damage to the windshield of the train but said no separate federal criminal investigation is yet under way. He said that NTSB officials interviewed engineer Brandon Bostian on Friday, and that he "cooperated fully." Bostian was accompanied by his attorney, who has said his client suffered a concussion in the crash. 
 
 Sumwalt said Bostian told investigators that the last thing he remembers is ringing a train bell as required as he went through the North Philadelphia station. He did not remember the crash. 
 
 Sumwalt said Bostian "did not feel fatigued nor did he report any illness." He said Bostian, 32, "demonstrated very good working knowledge of the territory, speed limits and things like that." Bostian drove the daily New York to Philadelphia to Washington, D.C. and back train run, Monday to Friday. 
 
 Sumwalt said that officials also had spoken with a conductor who "believes she heard her engineer say something about his train being struck by something," Sumwalt said. 
 
 "We have seen damage to the left-hand lower portion of the Amtrak windshield that we have asked the FBI to come in and look at for us," he added. He said the damage appeared in a "circular pattern that emanates out quite a bit." 
 
 Right before the crash Tuesday night at Frankford Junction, a SEPTA commuter train and another Amtrak train in the same area were hit by projectiles, one of which crashed through the SEPTA engineer's window. 
 
 The unnamed conductor told the NTSB she heard the engineer of her Amtrak train talking to the engineer of a SEPTA train about three to four minutes after leaving Philadelphia, Sumwalt said. The woman, a 39-year-old Amtrak worker, was in the fourth car - the cafe car - when she heard the radio conversation. 
 
 "She heard him talking to a SEPTA engineer who reported to a train dispatcher that he had either been hit by a rock or shot at," Sumwalt said, "and that the SEPTA engineer said he had a broken windshield and put the train into an emergency stop." 
 
 Sumwalt said the particular damage that NTSB wants the FBI to examine is the circular pattern of damage on the lower left windshield, as seen from inside the engineer's station. 
 
 He said the right-hand side of the windshield was shattered by the crash impact. 
 
 It was not known when NTSB agency would release a final report on the crash of Train 188. 
 
 Bill Shuster (R., Pa.), chairman of the house transportation committee, said Friday he planned to covene hearings on the accident. 
 
 In a statement, Amtrak president Joseph Boardman said, "Amtrak takes full responsibility, and deeply apologizes for our role in this tragic event." 
 
 Meanwhile, work to reopen the stretch of tracks where Amtrak Train 188 derailed, killing eight passengers, moved into high gear Friday, and service along one of the nation's most heavily traveled sections of rail was expected to resume Tuesday. 
 
 The Northeast Corridor is Amtrak's busiest, carrying millions of people annually, and the closure at Frankford Junction has halted Amtrak service between New York and Philadelphia and, by extension, New York and Washington. 
 
 It also has forced 12,000 daily riders who use SEPTA's Trenton Line to find alternate routes to work and has prevented NJ Transit's Atlantic City line trains from getting to and from 30th Street Station. 
 
 Officials say Train 188 had accelerated right before the crash and was speeding when it hit the sharp curve at the junction, jumping the tracks after the engineer activated the brakes. 
 
 Work is underway to replace 22 track panels along two of the four tracks at the site. Each panel is 60 feet long, Amtrak spokesman Craig Schulz said. 
 
 Crews also are installing four new catenary poles - the H-shaped steel structures that hold the overhead wires along the tracks. 
 
 "These guys have literally been working around the clock," Schulz said. 
 
 He did not have a cost estimate for the work, which also includes testing the signal and power systems. 
 
 He said crews will continue working around the clock until repairs are complete. 
 
 Against the backdrop of the work to reopen the junction and an ongoing investigation into the derailment, two dozen fire officials, police commanders and first responders gathered at City Hall to speak to about the massive city response to the crash. 
 
 The officials said it was an opportunity for the public to hear about the Herculean efforts that were undertaken to rescue wreck victims. The event began with a moment of silence for the dead and injured. 
 
 A dispatch supervisor spoke first, saying multiple calls came in from passengers on the wrecked train - who didn't know where they were. Officials used technology to identify the location of the cellphone calls. 
 
 "The people were frantic but they were also calm," said supervisor Ken Carey. "They were able to say, 'I've been in an accident, but I don't know where I am.'" 
 
 Repeated themes at the briefing were the horrifying scope of the disaster and the way the many responding agencies cooperated. 
 
 Back at the crash scene, a steady beeping of machinery and buzzing of cement trucks could be heard along Frankford Avenue on Friday morning. 
 
 Though the scene has been released back to Amtrak, it remained behind police barricades as repair work continued. 
 
 White Amtrak pickup trucks came and went from a dusty lot between two warehouses. Beyond the lot, dozens of workers in hard hats and orange vests labored along the tracks. Some later paused to paused to eat a lunch of chicken off paper plates in a parking lot along the tracks Friday afternoon. 
 
 Portable spotlights were in place for continuing work through the night. 
 
 Earlier Friday, bulldozers cleared the site where the front two cars - which were most damaged in the derailment - had crashed. Larger trucks also arrived on the site, where tents and portable toilets were set up in a staging area. 
 
 Six people injured in the derailment remained in critical condition - five at Temple University Hospital (down from six Thursday) and one at Penn Presbyterian Medical Center. 
 
 Officials have said more than 200 people were injured in the crash, about 150 of whom ended up in hospitals. 
 
 At a brief news conference outside Temple University Hospital, U.S. Sen. Robert Casey said he had toured the hospital to get a sense of the challenges facilities faced as victims of the Amtrak crash poured in. 
 
 He said he was "inspired by the really miraculous work that was done here under the most horrific of circumstances." 
 
 Inquirer staff writers Stacey Burling, Paul Nussbaum, and Mari A. Schaefer contributed to this article.
– The feds have interviewed the Amtrak engineer at the controls before this week's crash in Philadelphia, and while Brandon Bostian was fully cooperative, he says he still can't remember a thing about the derailment, reports CNN. But the more interesting development came from an interview with an assistant conductor, who said she thought she heard Bostian say before the crash that the train's windshield had been "broken by something,” reports the Philadelphia Inquirer. “We have seen damage to the left-hand lower portion of Amtrak windshield that we have asked the FBI to come in and look at for us,” says NTSB board member Robert Sumwalt. Prior to the crash, two other trains in the area had been hit by some kind of projectile, reports the Inquirer. One was a Southeastern Pennsylvania Transportation Authority train, and the assistant conductor remembers hearing about it. "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," says Sumwalt. "She also believed that she heard (the Amtrak) engineer say something about his train being struck by something." As for Bostian, he told the NTSB that he hadn't been sick or tired, but insisted he remembers nothing beyond the point his train left the nearby station in north Philly. (The train was clearly speeding up before entering a curve at twice the speed limit.)