Now, with the help of an elite course taught at West Point for members of the New York Fire Department, he's an expert.

"All the members of my company know that anguish, especially professionally, we felt after the attack," said Feehan, who on Wednesday will graduate from the course along with several colleagues. "Anything I can do prevent an event like that from happening again, I'm willing to do."

Firefighters and emergency medical services crews are already trained on the tactics of handling mass casualties, and in how to respond to an improvised explosive. The course at the U.S. Military Academy at West Point goes beyond tactics and into the theory and history of terrorism around the globe.

The class studied hypothetical scenarios like a chemical attack in the subway system, the detonation of a 1-kiloton nuclear device on Wall Street and a shutdown of the municipal water system. They pored over works by political scientists, government officials and other experts to understand the ideologies, causes and methods of terrorism. Students are expected to participate in lectures and average about 100 pages a week in reading.

"The feeling behind the course is that the more we can understand about the roots, the better we'll be able to combat it," Feehan said. "It really opened my eyes to things I had never thought about before. After 9/11, the focus was really on Islamic fundamentalism, but there is a lot of other stuff you have to be aware of out there."

The course was developed by West Point's Combating Terrorism Center, which analyzes issues around terrorism and makes policy recommendations. The class is taught in part by guest lecturers.

Feehan and 32 others will graduate Wednesday and will be expected to use their expertise within the department by developing recommendations for changes in Fire Department procedures that could help firefighters cope with an attack. So far, 172 members of the FDNY have graduated from the course, now in its fifth year.

Joseph Pfeifer, chief of the FDNY's Center for Terrorism and Disaster Preparedness, said the course targets middle managers in the FDNY who will eventually become department leaders.

"As they move up the ranks, they already have a serious understanding of the issue," he said.

Feehan is now the captain of Engine Company 249 in the Flatbush section of Brooklyn.

But on Sept. 11, he was assigned to Squad 252 in Bushwick and had the day off. The on-duty members responded at 9 a.m. to the fifth alarm at the World Trade Center, and all died. Feehan rushed to the scene from home, arriving just before the second tower collapsed.

In total, 343 firefighters were killed.

His father, First Deputy Fire Commissioner William M. Feehan, a 42-year FDNY veteran, was the highest-ranking fire official killed.