The inferno, which sparked at an ice cream shop around 2:30 p.m. and rapidly gobbled up around 50 businesses, turned the area into a hellish tinderbox.
"It's horrible. We're getting kicked while we're down," Seaside Park Police Chief Francis Larkin told NBC News. "It couldn't have come at a worse time for us."
NBCPhiladelphia.com reported that it took firefighters six hours to bring the flames under control. About 100 firefighters are continuing to battle hot spots Friday morning.
(Read more: Scenes from Superstorm Sandy)
Video footage captured by NBCPhiladelphia.com showed flames and thick plumes of smoke overwhelming the boardwalk in Seaside Park, a Sandy-hit town that was recently rebuilt in time for Memorial Day.
The blaze left Gov. Chris Christie emotional.
"This is obviously an unthinkable situation for us to be standing here and watching this," Christie said.
He later said, "I feel like I want to throw up."
(Read more: Sandy survivors face tough rebuilding choices)
That sentiment was common among locals dumbfounded by another blow to the community.
"I think this area has had enough of what nature and acts of God can cause," said John Condit, who has been coming to the shore for 15 years.
"I can't believe this is happening," Seaside Park Councilwoman Nancy Koury told The Associated Press as she watched the fierce flames tear through boardwalk buildings. "Our small business-people went through so much in the storm to get ready for summer and stay open all summer, and now it's all gone. I just can't believe it."
Christie and other officials declined to "speculate" on a cause for the fire, saying that their primary focus Thursday evening was stamping out the inferno.
"As soon as this is over, we'll pick ourselves up, we'll dust ourselves off and we'll get back to work," he said.
No one was seriously injured, although several firefighters did suffer from heat exhaustion and smoke inhalation, officials said
Kohr's Brothers, the ice cream shop where the blaze is believed to have begun, first opened on the boardwalk in Coney Island in 1919, according to NBCPhiladelphia.com.
It's since expanded up and down the East Coast in 10 states and is a well-known ice cream shop at the Jersey Shore.
—By NBC News Daniel Arkin and Alexandra Moe, with AP