Investigators said Erin Lindsay-Calkins, 26, failed to stop for crossing arms at the railroad crossing while turning from Forrest Drive onto Mount Willing Road in Efland December 22. The force of the crash killed her and her 5-year-old son Nicholas.
Lindsay-Calkins infant daughter Aven survived with only minor injuries.
Investigators say all the warning devices at the train crossing were functioning properly at the time of the crash. They said evidence that Lindsay-Calkins was on the phone was gathered from witnesses and Amtrak officials.
There are cameras mounted on Amtrak trains, but officials didn't say what the camera from the train that day showed.
Eyewitness Bessie Bean says she jumped out of her car and helped get the 4-month-old girl out of the totaled car and held the baby until paramedics arrived.
"I've lived next to this train for so long that I hear them, but I don't ? and now I hear it again, and my heart brakes," she said.
But Bean says something else about the crash has been haunting her - that police say Lindsay-Calkins was on her phone when she drove under the gate and onto the tracks.
"This was a tragedy," Bean said. "It was a human error."
According to the DOT, last year, on any given day, more than 800,000 vehicles were driven by someone using a handheld cell phone.
"After seeing this, it's brought a lot of awareness," Bean said. "Leave the cell phone in the seat beside you, leave it in your pocket book, wait till you get where you're going, pull off at a service station, and answer the phone or call the person back that was calling you. Don't ride down the road with that cell phone at your ear. It's a distraction."
There is currently an ongoing debate in North Carolina about a hands-free cell phone law.
A law went into effect just this month prohibiting texting while driving.