Lt. William McGinn, Sqd.18 Firefighting, not Engineering William E. McGinn was a civil engineering major at Hunter College. But he spent much of his spare time hanging out at the firehouse in Spanish Harlem where his uncle Kevin was a lieutenant. Some time around sophomore year, he took an exam that was not in any of his courses: the firefighter’s test. By the time he graduated, he had decided that being a civil engineer would be boring, so he became a firefighter. Eighteen years later, in September 2001, Firefighter McGinn was Lieutenant McGinn of Squad 18, a special operations command based in Greenwich Village, a father of two, cub scout leader and the only male member of the school leadership team at his children’s school in Riverdale in the Bronx. Lieutenant McGinn, 43, used his engineering skills mostly to demolish parts of the house, but he used them on the job, too. “He understood how structures and materials fail,” said Dr. Anne Golden, an epidemiologist, who was Mr. McGinn’s college sweetheart and who later became his wife. “He would have had a field day with this one.” Squad 18 was one of the first on the scene on Sept. 11 and lost all seven men, but Lieutenant McGinn had already passed on the firefighting itch. For the past two years, a kid from Staten Island named Sean Bradley spent much of his spare time hanging around Squad 18, where his uncle Billy was a lieutenant. Now Sean, 17, has decided that he wants to be a firefighter, too.