NEW YORK (PIX11) — Monday marks 22 years since thousands of people were killed in the terrorist attack at the World Trade Center in New York City.

Nearly 3,000 people died when 19 al-Qaida members hijacked four commercial airline planes, sending two of the planes into the Twin Towers and one into the Pentagon. The fourth crashed into a field in western Pennsylvania, never reaching the terrorists’ intended target.

In the two decades since the deadliest attack on U.S. soil, first responders who heroically spent time looking for people at ground zero, as well as those who spent months cleaning up the rubble, have dealt with serious and deadly health ailments, including cancer.

Family members of 9/11 victims gathered Monday morning in Lower Manhattan to read aloud their names and honor a vow to never forget.