the story behind the dramatic video of a stroller with a toddler strapped in as it tumbles on to an active train track in philadelphia. The mother and a good samaritan racing to the rescue and abc's... See More
the story behind the dramatic video of a stroller with a toddler strapped in as it tumbles on to an active train track in philadelphia. The mother and a good samaritan racing to the rescue and abc's john muller has the story. Reporter: The video is heart-stopping. A mother and her 14-month-old waiting on the subway i philadelphia wednesday when she looks away for a moment. Watch again, it takes seven seconds. The stroller slowly rolls towards the tracks. Then tumbles over the edge and flips upside down. The toddler still strapped inside. It's heart wrenching because you can anticipate it. Reporter: Without hesitating, the mother jumps on to the tracks as this woman pushes an emergency call button. Then as a good samaritan pulls the child to safety another man jumps on to the tracks to help the mother. One of our busiest lines and our trains run quite often. In this case, yeah, the stroller went into the track area at a time when fortunately there were no trains running. Reporter: This isn't the first time a stroller falling on to the train tracks has been caught on video. It happened at least twice before in australia. In 2009 and again in 2010 strollers rolled off platforms and landed under moving rains. Although the video is shocking in both of these incidents, the children were okay and this morning the philadelphia toddler seen here being taken by police officers and paramedics to a waiting ambulance is doing well with only a cut to her forehead. All witnesses say because the of brotherly love lived up to its name. For "good morning america," john muller, abc news, new york.
This transcript has been automatically generated and may not be 100% accurate.