25 years ago, a NASA astronaut witnessed the tragic 9/11 attacks from space. Here's what he saw.

Frank Culbertson had a birds-eye view of one of the most memorable and tragic events in American history.

The NASA astronaut was the only American off of Earth on Sept. 11, 2001. He was circling the planet aboard the International Space Station (ISS) when terrorists flew commercial jets into the twin towers of the World Trade Center in New York City, killing more than 2,700 people.

The ISS passed over New York shortly after the attacks took place, so Culbertson saw the devastation from an eerie remove. He shared his thoughts with Mission Control at NASA's Johnson Space Center in real time, chronicling the tragedy like no one else could.