A Goldman Sachs senior analyst vanished after leaving a New York City concert early Saturday morning, weeks after another man who disappeared from the same venue turned up dead, according to police and his friends.

John Castic, 27, was last seen about 2:30 a.m. outside The Brooklyn Mirage near the Williamsburg neighborhood of Brooklyn after an electronic music show, according to police.

A missing-person flyer says he was wearing a navy and white button-down floral shirt.

"One of my best friends, John Castic, went missing after the Zeds Dead show Friday night in NY," his friend, Sara Kostecka, wrote Monday on Facebook. "Any information would be greatly appreciated, as well as sharing this to anyone in NYC that might have seen him."

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John Castic poses with sun glasses next to a missing persons flyer for him.

Goldman Sachs senior analyst John Castic vanished Saturday morning after leaving a music venue in Brooklyn, according to police and friends. (Facebook)

She added that she had heard rumors about patrons being asked to "hop in a taxi/cab from some creepy people" near the music venue.

"I’m supposed to walk with him in my brother's wedding next week … we just want to find John," she added.

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He was reported missing Sunday, according to the NYPD. Another of Castic's concerned friends, Jonah Shlaes, told Fox News Digital that his phone died at some point after he left the venue and hasn't been on since.

"We’re absolutely very worried about him," Shlaes said. "No one has had any contact with him.

A gray and brick warehouse in Brooklyn.

John Castic went missing early Saturday morning after attending a concert at The Brooklyn Mirage, pictured. (LinkedIn / Google Maps)

Castic, who graduated from DePaul University, started working for Goldman Sachs about a year ago, according to his LinkedIn profile.

A representative for Goldman Sachs didn't immediately return a request for comment.

Another 27-year-old man tried to attend a concert at The Brooklyn Mirage on June 11 but was turned away because he allegedly appeared to have consumed alcohol, per EDM Identity.

The online publication, which covers the electronic dance music industry, reported that Karl Clemente was found dead in a creek near the venue a week later.

Karle Clement shown in three photos with a closeup of his tattoo sleeve.

A missing-person poster shows Karl Clemente, who disappeared after trying to attend a concert at The Brooklyn Mirage on June 11. He was found dead about a week later in a creek, according to EDM Identity. (EDM Identity)

Kostecka told Fox News Digital she has known Castic for seven years and that he has never been unreachable. She is fearing the worst.

"I know there’s been a series of young adult males, mid 20s, going missing and ending up in bodies of water in Chicago recently," Kostecka said, referencing the Smiley Face Killer theory. "I’m praying this isn’t related, but I fear it is."

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Citizen sleuths have speculated online that a serial killer is responsible for nearly a dozen bodies pulled out of the Chicago River and Lake Michigan in 2022.

The NYPD confirmed that Castic was reported missing but did not have an update on his case.