Within moments of the first bursts of gunfire inside a suburban Denver movie theater, the Reddit community was buzzing.

“Someone came into our theater at the midnight release of Dark Knight Rises and began opening fire,” read a posting on the user-generated news site by a “redditor” named Peener13. She described being in the theater next door in Aurora, Colo., when the shooting began and later posted a photo of her ticket to prove she was there. “Who here on Reddit can help me calm my nerves?”

The answer: thousands and thousands of people, who began adding comments to Peener’s thread on the site.

Others posted information, as well as misinformation. A Denver area user, known as integ3r, began blogging developments including police-scanner communications, well ahead of the first media reports:

1:27 [a.m.]: “Bring as much crime scene tape as you can”

1:28: “Aurora PD merging communications with Denver PD”

1:35: “Shooter wearing green camp pants”

1:37: “bomb squad is there, bringing in K-9 units. possible other bombs”

1:40: “18 ambulances on scene”

There was much more: eyewitness accounts, photos of victims, a link to a cellphone video on YouTube of panicked patrons streaming out of the theater.

Part community bulletin board, part worldwide crowd-driven info-machine, Reddit is a kind of Facebook or Twitter for news geeks. Unlike those popular social-media platforms, Reddit users eschew closed lists of “friends” or “followers” and post links, comments and news bits that are available to everyone in real time.

As a result, Reddit can turn citizens into instant journalists, enabling ordinary people who’ve experienced an extraordinary event to share it with the world without a printing press or broadcast tower. “You don’t need to be a big name or have a huge following,” Erik Martin, Reddit’s general manager, said in an interview. “On Reddit, what you post can be seen by hundreds of thousands of people very quickly.”

Or, with luck, even a few million. The site had 37.5 million unique visitors in June, according to Google Analytics, making it one of the most heavily trafficked news-and-discussion destinations on the Web.

During breaking events such as the Aurora shootings, Reddit becomes an ever-growing digital ant hill, with news and quasi-news from users piling up.

Soon after Peener13’s posting, for example, another Reddit user, themurderator, posted the following: “I am one of the 50 wounded in the aurora theatre shooting. here are a few photos of my very lucky but nonethless terrifying brush with death. my thoughts go out to those less fortunate than me.” The link led to a series of photos: someone holding a T-shirt with a jagged, blood-stained hole in it; a close-up shot of what appeared to be a bloody flesh wound from a gunshot; a bearded young man — apparently the poster himself — lying on a hospital gurney with dried blood near his shoulder.

Reddit, headquartered in San Francisco, was founded in 2005 by two University of Virginia classmates, Alexis Ohanian and Steve Huffman. They quickly sold it to Advance Publications, the owner of the Conde Nast magazine empire. The company, with only 20 employees, is independent, with Advance as its majority shareholder.

The site’s unique feature is that it lets registered users vote on which stories and discussions are important. Enough “upvotes” (approvals) pushes a thread to the top of the list, while “downvotes” sends it tumbling.

Beyond its eclectic front page, Reddit is subdivided into thousands of “subreddits,” online communities devoted to a specific discussion topic such as atheism, food or even tattoos.

No one is likely to mistake Reddit for a traditional news site. Its front page is a chaotic hash of stories and user-generated discussions. In addition to the Aurora tragedy Friday, one could find such headings as “My Lord Of The Rings Wood burned art” and “Albino python just hanging out.” All of it is displayed with the approximate visual finesse of a ransom note.

What’s more, Reddit’s biggest strength as an information provider — its crowd-sourced, real-time postings — are also its biggest weakness. While traditional news sources sometimes slip up (ABC News apologized for tying the alleged shooter to Colorado’s tea party), unconfirmed and inaccurate information regularly slips through on Reddit, as it did early Friday.

“Bomb . . . may have been confirmed,” posted Integ3r (later identified by Buzzfeed as Morgan Jones). “. . . Apparently a bomb may have blown up a part of a theater.” Later, he wrote: “1:55: New evidence for shooters. That’s plural. . . . Coordinated attack. Two shooters.”

Except there was no bomb and no “coordinated attack”; only one shooter was involved.

Despite the benefit of first-person accounts and a breadth of information,The drawback of sites such as Reddit is “you can’t be sure of any of it,” said Dan Gillmor, the founding director of the Knight Center for Digital Entrepreneurship at Arizona State University.

“You have to use judgment,” he said. “I think of these things like a picture being drawn. Whereas the overall picture is reasonably clear, many of the [details] are still being filled in. . . . It would pay for everyone in the media to take a breath. Slow news is like slow food. It has value.