Shortly before the explosion yesterday at the Boston Marathon, Wang Shi, the billionaire chairman of China Vanke Co., China’s largest real-estate development company, took a photo near the finish line. The subject was one of his 15 employees who participated in the race, wrapped in a Chinese flag, greeting family.

He posted it to Sina Weibo, China’s most popular social-media platform, at 2:49 p.m. Boston time, one minute before the explosions. He wasn’t heard from again until 3:12 p.m., when he posted a photo of the scene. Smoke rises over the street as confused spectators appear to move in the opposite direction. Wang wrote: “Two loud bangs near the end of the course, race terminated, evacuating.”

Elsewhere on the 500 million-member Sina Weibo service, Boston-based Chinese nationals -- many of them students at universities there -- were also busy reporting the story. At 2:55 p.m., an anonymous user in Boston asked: “Did an explosion occur? Boston Marathon.” At 3:01 p.m. another Boston-area Sina Weibo user wrote: “Goodness, I was close to the finish line of the Boston Marathon where there were just two explosions.” One minute after that, JingChuiSh, another Sina Weibo user in Boston posted an image of police blocking off an area, writing: “Police coming from all directions to Copley Square, heard an explosion, the shopping mall has closed its doors.” After that, tweets and retweets of news and rumors spread across the largely Chinese-language site.

In China it was 2:50 a.m. when the bombs went off, so there weren’t many netizens awake and watching the news, much less paying attention to a rare instance of Chinese microbloggers covering an overseas breaking news event. China’s traditional, state and Communist Party-run media didn’t cover the story until dawn. Even the Sina Weibo account associated with CCTV America, the North American branch of China’s flagship television network, didn’t report the news until 5:48 p.m. in Boston. Chinese, especially those in the U.S., looking to traditional Chinese news media didn’t have many options.

Chinese microbloggers who couldn’t report the story firsthand turned to foreign news media and social media, including Twitter, which is censored in China, and started translating the considerable flow of fact and rumor. At 4:08 p.m. Le_Frank, the handle of a Belarus-based Sina Weibo user posted: “Twitter: Boston police found other bombs. Asking people to immediately get away from the Marathon.” Photos and video from non-Chinese sources quickly multiplied during the 4 a.m. hour in China, and by 5 a.m., Chinese netizens had access to almost as much Chinese-language information about the bombing as someone sitting in a U.S. Internet cafe.

The alacrity and freedom with which the traditional U.S. media, and its social-media commentators, gathered and distributed information on the Boston attacks didn’t go unnoticed by Chinese nationals in the U.S., or in China, especially by those who work in news media. At 6:13 p.m. “Pretending to be in New York,” the anonymous handle for a Chinese microblogger who identifies his location as “overseas” posted his reaction to how the U.S. government and citizens were handling the crisis, drawing a comparison to the tight control that Chinese officials typically exert over news stories on politically sensitive tragedies in China.

“Three hours after the Boston bombing: the websites and televisions have live scrolls, not publicity bans; police hold a news conference immediately to react to information and be transparent and, as a result, there is no panic; Google established a person finder,” he wrote. “The positive interaction of major public events, government, media, businesses, citizens, is something we should learn from.”

By U.S. standards, this transparency and coordinated reaction is expected. But in China, it’s trenchant social criticism that generated a jaw-dropping 51,000 repostings by Tuesday night in China.

The Chinese reaction had the potential to turn political. In the days after the Sept. 11 attacks, many Chinese publicly celebrated them as a justified humiliation of a bully, and the memory of that bitter outpouring remains a source of embarrassment. Fortunately, the Boston attack, far from inflaming the deep antipathy that many Chinese feel for U.S. foreign policy, appears to have inspired a widespread outpouring of empathy. “As Chinese, we are praying for you,” tweeted a Beijing-based graduate of Bentley College. “I almost went to the marathon,” a music student wrote. “Here’s wishing peace to all of the students in Boston.” Sister Ran Xiang, the handle for a popular microblogger in Guangzhou, wrote:

“Years ago, the whole of China applauded 911. Now in the wake of the Boston Bombings, we see a lot of sympathy and condemnation. A moment of silence for the dead and wounded and a prayer for the continued recovery of China’s humanity.”

Her tweet is followed by seven emoticons depicting flickering candles, a common way of memorializing the dead on Chinese social media.

Yet the mood is unlikely to remain entirely reverent. Speculation over whether the attack was the work of the North Koreans is common -- and heavily censored. At the same time, many microbloggers, ever-suspicious of U.S. foreign policy motives, cite the U.S. attacks on Afghanistan and Iraq to suggest that the U.S. might use Boston as an excuse to attack North Korea.

Despite the conspiracy theories, much of the postings on Chinese social media were in support of the city of Boston and those affected by the bombing. A single post by the Sina Weibo account for LobsBoston, a Boston-based website that caters to “the large number of Chinese residents in the greater Boston area” has been reposted more than 700 times by microbloggers almost exclusively in China, many of whom left comments citing concern for their friends in Boston.

“Boston is the best city in the U.S. and the world regardless of the criteria used. It has the best university, the most legendary teams,” the post said. “Many people don’t like LA or New York, but nobody can deny Boston. I love Boston, and I pray for you.”

(Adam Minter, the Shanghai correspondent for the World View blog, is writing “Junkyard Planet,” a book on the global recycling industry. The opinions expressed are his own.)

To contact the author of this article: Adam Minter at ShanghaiScrap@gmail.com.

To contact the editor responsible for this article: Kirsten Salyer at ksalyer@bloomberg.net.