BEIJING — Her red armband says it all: “On duty.” From her perch behind the window of a small guard post, 71-year-old Wang Aiqing keeps a careful eye on the comings and goings at the apartment complex where she lives in the capital city’s Chaoyang District.

For the past decade or so, Wang has belonged to a vigilante group that Chinese netizens have nicknamed the “Chaoyang Qunzhong,” or “Chaoyang Masses.” These volunteer guards sign up through their neighborhood committees — the smallest political unit of the Communist Party — to surveil the area for crimes ranging from the sale of stolen e-bikes and street corner scams to narcotics dealing and potential terrorist threats.

Beijing has 130,000 registered members of the Chaoyang Masses, reported the Beijing Morning Post. Some 60,000 of these are considered active participants, averaging more than 20,000 police tip-offs per month.

Chaoyang measures 470 square kilometers and is the most populous district in the capital. Foreign embassies, international media organizations, and financial and cultural institutions are stationed here, and it’s also home to many of China’s top celebrities. All told, maintaining public order is a challenge, and the police appear happy to have the extra support of the Chaoyang Masses.

In February, Chaoyang District police launched the Chaoyang Qunzhong HD app as a platform to help law enforcement and volunteer guards communicate. The police can assign cases, and members of the Chaoyang Masses can post messages, photos, and videos to report violations.

In recent years, the civilian team has uncovered information leading to the arrests of celebrities involved in drug scandals, among other criminal investigations. In the first 10 months of 2015, tip-offs from the Chaoyang Masses helped the police crack 1,023 cases and detain 810 suspects in various crimes. Netizens have referred to the group as “the world’s fifth most powerful intelligence agency.”

The Chaoyang Masses are not the only example of Beijing law enforcement enlisting the help of ordinary citizens. In 2014, the city launched a campaign to reward residents for reporting activities related to terrorism. Rewards are split into three levels, with the lowest level awarding tipsters between 1,000 and 10,000 yuan ($148-$1,488).

Typically, members of the Chaoyang Masses are retired factory workers between 60 and 75 years old. When she was younger, Wang also worked in a factory. “My generation is one educated by Chairman Mao to work hard without complaining, work diligently and conscientiously, and be willing to undertake all tasks,” she says.

In the beginning, Wang’s children didn’t support their mother’s volunteer activities; they reminded her of her age and tried to persuade her to stay home. Once, when Wang was patrolling the neighborhood on a snowy day, she slipped on a patch of ice and suffered a concussion. Afterward, she had to spend six months on an IV drip — but she is determined to continue serving.

After receiving an assignment from her neighborhood committee, Wang and fellow Chaoyang Masses volunteers take turns patrolling the immediate vicinity of their compound, usually in two-hour shifts. If she notices anything out of the ordinary, she notifies either the community police or the neighborhood committee.

The 5-square-meter guard post at the compound entrance is headquarters for Wang and her fellow vigilantes: It’s where tasks are assigned and detailed plans laid. From here, the volunteers have a sweeping view of every exit and entrance to the small community.

The volunteers’ minds are like databases that hold information on almost every member of the community: Are they a homeowner, or do they rent? How many members are in their household? Where do they park their car? And as soon as a Chaoyang Masses guard spots a stranger in the compound, they are instantly on alert.

According to Hou Xijun, chairperson of the neighborhood committee for Wang’s area, attracting new volunteers to the Chaoyang Masses is easy. “These residents have a strong sense of political responsibility,” he explains. Hou adds that locals often gather to talk about current issues, including geopolitical topics like the South China Sea. “Residents of Beijing care a lot about the capital’s security and stability,” he says.

In Hou’s eyes, there is an advantage to having senior citizens carry out surveillance duties, as they can easily elicit sympathy from others. He often reminds Chaoyang Masses members of the importance of their work: “This is for the honor of Chaoyang District, the honor of Beijing, and the honor of the capital,” he says.

Ma Hongrong, 65, used to serve as a leader of the Chaoyang Masses team in her neighborhood. During the 2008 Beijing Olympics, she organized a group of volunteers to monitor her apartment complex and its surrounding streets. She has since temporarily left the group to help take care of her grandson, but her commitment to the civilian force has not wavered.

Ma doesn’t know how to use the internet; she doesn’t know that “Chaoyang Qunzhong” has become a trending term on social media. However, when asked about the group, she cheerfully replies, “Of course I’m part of the Chaoyang Masses. Don’t I live in Chaoyang District?”

Translator: Christine Liu; editors: Fan Yiying and Colum Murphy.

A Chinese version of this article first appeared in Sixth Tone’s sister publication, The Paper.

(Header image: A volunteer guard with a red armband walks down the street in Beijing, Sept. 2, 2015. Wang Kaichicn/IC)