The retired MTA employee has pumped $140,000 into a NYC Transit ad campaign to warn everyone the world will end next Saturday.
"Global Earthquake! The Greatest Ever - Judgment Day: May 21," the ad declares above a placid picture of night over Jerusalem with a clock that's about to strike midnight.
"I'm trying to warn people about what's coming," the 60-year-old Staten Island resident said. "People who have an understanding [of end times] have an obligation to warn everyone."
His doomsday warning has appeared on 1,000 placards on subway cars, at a cost of $90,000, and at bus shelters around the city, for $50,000 more.
Fitzpatrick's millenial mania began after he retired in 2006 and began listening to California evangelist Harold Camping's "end of days" predictions.
Using head-spinning numerological calculations, Camping has determined that the world will end on Saturday, May 21. He's used similar biblical math to pinpoint when Abraham was circumcised (2068 B.C.) and when earth was created (11,083 B.C.).
Camping has predicted the end of world once before - on Sept. 6, 1994. When the sun rose on Sept. 7, Camping admitted he might have had that one wrong.
Still, Fitzpatrick remains convinced the beginning of the end is coming next week.
"It'll start just before midnight, Jerusalem time: It'll be instantaneous and global," he said. "There are too many scriptures talking about 'sudden destruction.'"
While Jesus Christ returns to Earth and all non-believers burn in eternal hellfire, Fitzpatrick says he and all those in the know will be saved in the rapture.
Similarly convinced followers around the city have taken it upon themselves to spread Camping's doomsday prediction to anyone who will listen.
"We're just heeding the warning God gives in Ezekiel 33 that God has appointed true believers as watchmen," said Esteban Ramsey, 19, of Harrison, N.J., as he handed out literature with fellow believers in Union Square this week.
Most dismissed the warning as the ranting of lunatics.
"I'm curious to see what they're going to say in a week when nothing happens," said Mollie Kotzen, 23, of Prospect Heights, rolling her eyes as she passed the group in Union Square.
Camping's group bought billboards in other parts of the country around Christmas time, but Fitzgerald is financing the New York ad campaign on his own, saying he wants to take as many people with him as he can.
The MTA says they have no problem with it.
"It's an individual's prerogative to spend their money as they see fit," said MTA spokesman Kevin Ortiz.
Anti-religion groups say the MTA should never have allowed the ad blitz.
"Doomsday cults are money-making enterprises," said David Silverman, of the American Atheists group, which ran counter-ads to Camping's earlier billboard campaign.
"I wonder what is going to happen on May 22 when people no longer have their possessions or their savings and we are all still here and they don't have their rapture," he said.
Fitzgerald said there's no chance that will happen and he has had no doubt about plunking down his retirement.
"It is the date," he insisted.
Not that he's been able to convince everyone.
"My sister doesn't believe it," he admitted. "I've tried to tell her. But that's pretty much the story with most people."