Downtown St. Paul's longest-running jazz space has been unplugged again.

The operators of KJ's Hideaway -- in the basement of the Hamm Building where the Artists' Quarter and Vieux Carré used to be -- abruptly announced the venue's closure on Monday, effective immediately. It sounds like the shutdown could be permanent, too.

"Thank you to everyone who has come and supported us in our mission over the years," read a message on the club's Facebook page, which cited "unexpected emergent personal matters."

Owner and operator Jeremy Siers declined to comment further. He is promising refunds to ticket holders for canceled shows.

Siers opened the venue coming out of the pandemic in late 2021 with his wife, Kristen Siers (the "K" and "J" came from their names). The couple were regulars at the club there before KJ's, Vieux Carré, which had been operated by the same team as the Dakota in Minneapolis.

With the long-beloved Artists' Quarter, too, the space downstairs at 408 St. Peter St. has hosted jazz gigs for more than 20 years. As KJ's, it also began hosting rock, country and singer-songwriter acts as well as a popular Wednesday open mic night.

Among the many Twin Cities music scene members surprised by the news was country-rocker Ken Valdez, who played to a packed house on Sunday night just 12 hours before the announcement was made.

"We had a great time, and it seemed like everything was fine there," said Valdez.

Trumpeter and bandleader Steve Kenny -- who booked the Saturday night jazz series at KJ's -- also said the venue seemed to be doing OK financially and was seeing well-attended shows over the past year. New neighboring businesses, including St. Paul offshoots of the Loon Café and Wrecktangle Pizza, have helped bring back some pre-pandemic traffic to that corridor of downtown.

Kenny said he only found out about the plans to close on Sunday and was still trying to make sense of it.

"Ultimately, I think it had nothing to do with how the business was doing and more to do with the owner just wanting out," he said.

Kenny said some of the upcoming concerts -- which had been booked as far out as December -- could wind up moving to new locations, including a gig scheduled Saturday with reputable Detroit saxophonist JD Allen and the Cody Steinmann Trio. Contingency plans also will likely be made for concerts planned there during the Twin Cities Jazz Festival in June.

New owners could possibly take over the space, but both Kenny and Valdez lamented the exit of these particular owners.

"They always had the best of intentions and we're willing to try new things there," Valdez said. "They'll be missed."