A New York-bound Amtrak high-speed Acela train traveling through Bridesburg just before 7 p.m. Sunday was hit by something that smashed a coach window.

The incident came the day before the federal investigators are slated to release hundreds of pages of documents in their probe of the crash of an Amtrak train in May in nearby Frankford that claimed the lives of eight people.

After the object slammed into the window Sunday night, one startled passenger tweeted that a bullet hit the train, but Amtrak officials said Monday morning they haven't determined what the object was.

Taylor Lorenz, 30, a freelance editor from the Park Slope section of Brooklyn, was on the train, a few seats from the broken window.

"We were just riding along as normal, and all of a sudden, there was a really loud sound, like a big boom," Lorenz told Philly.com this morning. "Everybody just looked around, like: 'Whaaaaat?!' It sounded like a tray table being smashed really loudly, or something hitting the train from above the train. Where it hit, it looked like a bullet hit the train, like something pointy, not rounded, hit the glass. Somebody said: 'Somebody shot the train!'"

The train stopped at the Metropark station in New Jersey, where Amtrak police boarded to investigate. After about a half hour, they deemed it safe to continue to New York.

"The conductor came over and said: 'Yeah, this has happened before.' He said: 'Don't worry, the glass is really strong,'" said Lorenz, who had boarded the train in Baltimore.

"We were like: 'What the hell, Amtrak?!'" Lorenz said. "And because we were going through Philly, we were like: 'Of course this would happen in Philly.' Baltimore is so sketchy. I was just glad it didn't happen in Baltimore, because people are always throwing shade on Baltimore."

Amtrak spokeswoman Kimberly Woods said this morning: "Amtrak is investigating an incident of objects thrown at Acela Express 2222 in Bridesburg, Pa.

"The incident was reported at 6:55 p.m. on Jan. 31. At the time of the incident, 201 passengers were on the train. There are no reported injuries to passengers or crew members. Amtrak and local authorities are investigating the incident.

"A window was damaged and it will be inspected as part of the ongoing investigation to determine what objects hit the train."

The train originated in Washington and arrived in New York around 8 p.m.

National Transportation Safety Board officials are expected today to release more than 2,000 pages of documents and evidence relating to the May 12 deadly derailment of Amtrak 188 in Frankford.

The cause of that crash remains unknown, although one theory was that the train had been hit by an object, startling the engineer and causing him to speed up through a curve where the train crashed.

Lorenz said last night's drama wasn't her first on Amtrak.

"I feel like I've seen it all," said Lorenz, who travels the route twice a week. "My Amtrak train hit and killed someone in July. But I'll keep taking it, because it's the only way to get around. I don't have a car, and the bus sucks."