A historic Manhattan cathedral was gutted in a blaze hours after its Serbian Orthodox parishioners celebrated Easter on Sunday

The fire started Sunday evening and quickly engulfed the Serbian Orthodox Cathedral of Saint Sava in the Flatiron District, the FDNY said.

More than 700 parishioners had celebrated Easter earlier in the day and enjoyed a luncheon, but the cathedral was empty when the fire started.

A building caretaker attempted to rush inside when he noticed the fire, but was turned back by the flames, fire officials said. He suffered from minor smoke inhalation.

Five other people, including four firefighters, also had minor injuries, according to fire officials.

Onlookers watched in horror as flames shot from stained glass windows.

"It was apocalyptic. Very frightening. And it's a shame," said tourist Herman Tulp.

Members of the Serbian community that worships at the church called the blaze heartbreaking.

"It means the world to me and to see it [...] I was just here four hours ago for Easter," parishioner Jovana Djurdjevic said as she cried.

Flames shooting from Cathedral of St. Sava on 25th in #NewYork. No word on injuries. pic.twitter.com/pGJRhrLbWO — Bob Redell (@BobNBC) May 1, 2016

Witnessing a huge church fire in flatiron. Flames billowing out. Rood pouring the smoke. Completely engulfed. pic.twitter.com/8qJfgc2zcE — Mollie Tavel (@MobileMollie) May 1, 2016

"This loss is epic. An epic tragedy," another parishioner said.

A church priest, the Rev. Djokan Majstorovic, told The Associated Press that he felt like he was "in a nightmare" as he tried to get to the fire scene that was blocked off by firefighters.

"This church brought everyone together, because although there are Serbian churches in New Jersey, this is like the only one in New York," Djurdjevic. "This is absolutely horrible. Absolutely horrible. My heart is completely broken."

Fire officials said portions of the roof had collapsed and the structure was unstable and in danger of falling down.

The fire continued to burn overnight and crews were still dousing hot spots throughout Monday morning. The blaze was fully extinguished by about 2 p.m.

Investigators say the cause is still under investigation, but fire marshals are looking into whether candles might have been to blame.

Three other Orthodox cathedrals burned the exact same day around the world -- one in Russia, two in Australia -- but police said there's no evidence they are linked. The fire is not thought to be suspicious in nature.

"I just hope it was a candle left out, forgotten somehow," said parishioner Luka Vojdodich. "It was a very old church, it had a lot of wooden pews and carpet, very dry, so it probably went up in flames very quick."

The cathedral, formerly known as Trinity Chapel, was designed in 1850 by architect Richard M. Upjohn in the Gothic Revival style.

The chapel was an Episcopal Church for several decades until 1915, when the area became more commercial and parishioners decided to relocate.

The Serbian Orthodox Church purchased the structure from the Episcopal Diocese in New York in 1943.

The church, on West 25th Street was designated a New York City landmark in 1968.

And despite the destruction, Vojdodich couldn't help notice Monday the flags out front remained intact.

"The flag is still standing, which I think is pretty incredible," Vojdodich said. "I don't even know how that's even possible with all the blaze... That's the meaning I would like to give it."