Ten years ago, 19 men trained by al-Qaeda carried out a coordinated terrorist attack on the United States that had been planned for years. The attackers simultaneously hijacked four large passenger aircraft with the intention of crashing them into major landmarks in the United States, inflicting as much death and destruction as possible. Three of the planes struck their targets; the fourth crashed into a field in Pennsylvania. In a single day, these deliberate acts of mass murder killed nearly 3,000 human beings from 57 countries. More than 400 of the dead were first responders, including New York City firefighters, police officers, and EMTs. It was one of the most-covered media events of all time, and after a decade, the images are still difficult to view. These attacks and the global reaction to them have profoundly shaped the world we live in, so it remains important to see the images and remember just what happened on that dark day. This entry is part two of a three-part series on the 10th Anniversary of the 9/11 Attacks -- (see also Part 1: The Week Before and Part 3: The Decade Since).