When retired journalist Zhou Xiaoxiang started a WeChat group on Friday, he had no idea it would set in motion rescue efforts for an earthquake the next day.
Half a week later, more than a hundred charities, activists and donors have joined the conversation, which has turned into an umbrella organisation for NGOs and co-ordinates local donations for earthquake victims in Sichuan.
"I never expected that we'd have this earthquake the next day," said the Chengdu-based executive director of an NGO that helps miners with lung diseases. "In the first two hours after the quake, all the phone lines were down, we could only talk on WeChat. This was our opportunity."
The WeChat group consisted of about 50 welfare organisations, 30 funds and 20 media organisations, Zhou said. Several government departments are also part of the closed group, but "they are just watching what we are doing, they are not interfering".
Zhou's group has created a civil movement offering help to quake victims. Its mere existence would have been unthinkable in the aftermath of the 2008 Wenchuan earthquake, Zhou said. It happened only because of the changes in social media over the last years.
The WeChat group, Chengdu Public Welfare Circle, was originally meant to bring together social welfare organisations in the city and train them in using microblogs and WeChat, an instant-messaging application for smartphones.
"Someone jokingly said that old Zhou can predict earthquakes," said Fu Yan, a volunteer with Yungongyi, another WeChat group that is partly funded by the government and that followed Zhou's lead on Saturday.
Chengdu's phone network was paralysed after the earthquake, but WeChat was still operating. "There was chaos, and we didn't know how to respond. We were lucky to have that WeChat group," said Fu. "All the leaders of social welfare organisations were in it and could discuss how to react."
Within hours on Saturday morning, the groups decided on a venue to collect donations and spread the news to their organisations, friends and on their own microblogs.
By 8pm, the first truck carrying rescuers left Chengdu for the earthquake zone some 200 kilometres away. The truck arrived by 1am.
In the same evening, Narada Foundation, a charity financed by a Zhejiang-based property developer, pledged to cover costs for the rescue transport up to 20,000 yuan (HK$25,000). The next day the charity increased its pledge to 200,000 yuan.
"Civil society is changing. The government has realised that it can't get everything right," Zhou said. "In 2008, NGOs were chaotic, unprofessional and they couldn't co-ordinate."
"We all knew each other and the authorities knew us too," said Xu Qizhi, another participant in Zhou's group. "Because of that, we were among the few given an entry permit into the disaster zone."
The State Council had banned volunteers and non-essential rescue staff from entering the disaster zone on Saturday. The permit gives the group rare access and implicit government approval that others have not been so lucky to get.
A thousand volunteers were asked to leave Longmen township alone, Beijing News reported  on Tuesday. Many of them were students from nearby universities who lacked expertise to be of use in the search-and-rescue efforts.
On Sunday, the umbrella organisation born out to the WeChat group had already sent volunteers on motorbikes to the disaster zone and set up first-aid camps.
By Tuesday, it had sent 23 trucks of supplies, Fu said.
A team of 10 to 15 experienced volunteers intended to stay in the disaster zone for one month, employing local people in the rescue, said Xu. He said they were hoping to collect funds so the group could participate in the reconstruction of the village.
"Our advantage is that we are on the ball, and the government isn't as much," said Zhou.
"We want to expand this to the whole country, but we first have to get this thing right," Zhou said. "We just have to prove ourselves in this critical moment."