At the beginning of 2016, our organization received a shocking video on DefeZap, a mobile WhatsApp channel we had just developed to allow people in Rio de Janeiro to report state violence. The video showed the police tossing the body of a young man into the bed of a pickup truck. We later learned the man was Igor Silva, 19, killed that morning by the civil police’s elite unit in the neighborhood of Maré.

The video was in direct contrast to the story provided by the police—that Silva had been carrying a gun and had died while being taken to the hospital after being wounded in a shootout with police—which was published on the front pages of the country’s biggest newspapers [link in Portuguese].

We forwarded the video to the public prosecutor in hopes that the office would investigate the case. Once an inquiry was opened, we also forwarded the video to a number of national and international media outlets that reported on the case so they could correct the stories they had published previously.

We were still in the testing phase of DefeZap, but the speed with which the video reached us was our first indication of the usefulness of the tool and its everyday convenience for cariocas, or citizens of Rio, who might need to defend themselves from the state. In Rio de Janeiro, scenes of executions by the authorities are often altered to make it look as if they were providing aid. Police remove bodies before forensic examinations can be conducted, skirting official orders to preserve crime scenes until experts arrive.

DefeZap is led by a journalist and lawyer who catalogs the videos and then forwards them to government oversight bodies. DefeZap then monitors the actions the agencies take and keeps the user informed as to any progress. Videos can be sent via a WhatsApp number or uploaded through a website.

The channel eliminates the normal bureaucratic process of filing a complaint and waiting for it to be investigated. It also allows users to remain anonymous—critical in a city where the authorities can be a threat.

DefeZap is not an app; it is an automatic referral system that connects to existing apps. Our initial thought in developing the tool was that citizen participation would be an important contribution to decreasing the extremely high rates of violence the state exercises against its citizens in Rio de Janeiro. Between 2010 and 2015, more than 3,250 people were killed by the police in our city.

Nossas Cidades has specialized over the years in developing networks and platforms for mobilizing citizens to produce changes in public policy. One of the members of our network, Meu Rio, has more than 200,000 affiliates and has led to 50 public policies established or amended based on complaints from cariocas.

In developing DefeZap, the first issue we identified was that it would be difficult to convince Brazilians to add new apps to their daily routines. Who would download an app for reporting police violence: the people who really experience it, or only niche activists? Would it really reach the users in the favelas and outlying neighborhoods?

Interviews with test groups of potential users confirmed what we’d already seen in surveys of the Brazilian market: WhatsApp, a free messaging service, dominates Brazil’s private communications market; it is also the app used most for sending video. When WhatsApp moved to secure its users with end-to-end encryption at the end of last year, we decided to dedicate our resources to building a database for organizing and monitoring the report that could become a part of cariocas’ routines organically.

In February, we tested DefeZap among a network of partners in the areas most affected by state violence. That’s how the video of Igor Silva, from Maré, came to us on February 22. We received five more cases before the project launched publicly on May 9.

In its first six months, DefeZap received more than 102 videos, from which Nossas Cidades identified 57 different instances of state violence. Of these, 42 involve the military police, 22 were recorded during police operations in favelas, 16 show explicit state violence, 10 show situations where lethal violence was used, and 9 show police repression of peaceful protests.

The videos also confirm well-known statistics: the majority of victims are young Afro-Brazilian men from impoverished communities. Based on the videos, Nossas Cidades made 32 formal complaints of police brutality to external and internal accountability mechanisms, resulting in 20 official inquiries being launched.

We believe strongly that state violence persists because people have not previously had the tools to ensure that institutions existing “in law” also exist “in fact.” DefeZap is still taking its first steps, but the success of its first six months in operation tells us we’re on the right track.