Caps fans during an Eastern Conference finals watch party. (Astrid Riecken for The Washington Post)

Tickets to the Capital One Arena watch party for Game 5 of the Stanley Cup finals vanished within minutes Wednesday afternoon, amid massive demand that far outstripped the arena’s capacity.

More than 70,000 people went online at 1 p.m. Wednesday in search of free tickets to the Thursday night event, which were claimed “almost immediately,” according to Monumental Sports and Entertainment. Fans were limited to two tickets each, and with skyrocketing demand, online listings soon appeared offering the free tickets for hundreds of dollars.

“The growing crowds each night at the Game 1 and Game 2 watch parties meant that we needed to ticket Thursday’s event in order to ensure that we could keep everyone safe and that people could enter and exit the Arena in an orderly way,” the organization said in a statement. “We thank everyone who jumped online to get tickets and we hope that everyone who wasn’t able to get a ticket to the indoor viewing party still comes down to the Arena on Thursday night to watch the game together outside on the jumbotron at 8th and G Streets.”

The watch party giveaway set the stage for one of the wildest afternoons in that arena’s history: The Capitals could win their first Stanley Cup in Las Vegas on Thursday night, but first comes a previously scheduled Mystics game that seems likely to attract a virtually unprecedented WNBA crowd. That game was moved up from 7 p.m. to 4 p.m. last week, prompting some Caps fans to snatch up Mystics tickets in hopes of ensuring entry into the watch party. (Ticketed Mystics fans will be able to remain in their seats for the watch party, Monumental said, although no reentry will be permitted.)

The organization announced Tuesday that while previously purchased tickets to the Mystics game would be honored, their cost would be refunded and no other tickets would be sold. Instead, Monumental instructed Caps fans to queue up for free online tickets to the watch party starting at 1 p.m. on Wednesday.

But as fans attempted to access those tickets, many found only a spinning wheel or an error message and never got seats. At 1:20, the Caps announced the free tickets were “sold out.”

As frustrated fans complained about the situation, others suggested the creation of a second watch party at Nationals Park. The Nats are off Thursday. Wednesday evening, the U.S. Navy Memorial — on Pennsylvania Avenue, down 7th Street from the arena — announced that it was postponing a scheduled screening of “Anchors Away” and would hold a watch party on its jumbo movie screen.

Game 5 will also be broadcast on video boards located outside Capital One Arena on G Street and 8th Street NW, as was the case for Games 3 and 4.

Admission to the watch party is general admission, first come, first served, according to Monumental, which could create a chaotic scene during the Mystics game. And with the watch party tickets sold out, some entrepreneurs offered Mystics tickets for hundreds of dollars Wednesday, guaranteeing the purchaser a different way into the watch party. Others were pleading for such tickets.

“Caps watch party tickets sold out in minutes while I was stuck in the queue,” wrote one in an online post. “Big Caps fan wants Mystics tickets anywhere in the arena. Please call or email me.”

“I’m a die-hard, lifelong Caps fan hoping to buy two tickets for the Mystics game tomorrow,” wrote another. “Please email me; will respond very promptly.”

A Mystics season ticket holder, meanwhile, was offering two tickets and a parking pass to the game for $500.

More than 14,000 Capitals fans turned out last Wednesday to watch Game 2 of the Stanley Cup finals, also played in Las Vegas, on the Capital One Arena video board. Thousands more have filled the streets outside the venue for the last two home games. The Mystics drew a season-high 7,400 fans for their home opener last month and 5,176 for their most recent home game.

The Mystics on Thursday will face the defending champion Minnesota Lynx, who spent Wednesday in Washington doing community service after not receiving an invitation to the White House. Doors for the Mystics-Lynx game will open at 3 p.m.

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