The moment of impact from the Amtrak crash that killed at least seven people and injured more than 200 others was captured on grainy security camera footage Tuesday night.
The brief and shadowy black-and-white video shows multiple flashes of bright light as the train derails.
Residents in the Port Richmond neighborhood of Philadelphia, where the crash happened, told NBC News they saw a "big flash."
"I thought it was lightning, but it was kind of bright," Adele Lafferty said. "Next thing you know, the whole street was filled with cops."
Matt Munzo said he had never seen anything like it before.
"There was a big flash in the sky," he said. "It lit up the whole sky, can't describe the sound."
The National Transportation Safety Board, which is investigating the crash, said on Wednesday that Amtrak Regional 188 was barreling ahead at a speed of more than 100 mph as it rounded a curve where the speed limit dropped from 70 mph to 50 mph.
The train was going from Washington, D.C. to New York when it derailed shortly after 9 p.m.
Father and son team Harry Krings and Chris Krings, 16, were on their way home from a grocery store just blocks away when the crash happened.
Harry said it was just "a big flash of light and a lot of noise."
"People (were) yelling out, 'Please can you help us, can you get us out of here, help please?'" said Chris.
"I Helped a pregnant female, she had hurt her side," said Harry. "And uh, she was more worried about people in the train injured than about her own self."
IN-DEPTH
- Train Was Going Faster Than 100 mph, Sources Say
- Navy Midshipman, AP Staffer Among Dead
- Survivors Recount Amtrak Derailment