A masked Moscow riot cop gut-punched a woman last Saturday. Now there’s a 100,000-ruble reward for information leading to his name.

Following Moscow’s mass opposition protest on August 10, some demonstrators decided to stage a march through the center of the city. Many of these people were arrested in the Kitai-Gorod region, and police arrested a total of 256 activists before the end of the day. Replaying scenes from multiple protests in recent weeks, police responded with overwhelming force, pinning protesters’ arms behind their backs, dragging them into police vans, and officers beat at least one person in custody.

On Zabelina Street, the police arrested a man who is apparently disabled (a correspondent from the television network Dozhd says the man has mobility problems). While carrying him to a police van, the officers also dropped him.

Later, as two other police officers dragged a young woman to a police van, one of the officers lost his club, and punched the woman in the stomach, before picking it up. Eye witnesses filmed both the disabled man’s arrest and the gut punch to the young woman.

The disabled man’s identity is still unknown, but the woman who sustained a blow to the stomach is Darya Sosnovskaya. She is now charged with the misdemeanor offense of violating Russia’s laws on public assemblies.

The “Zona Prava” human rights organization says Sosnovskaya has filed charges against the officer who attacked her. According to her lawyer, Tatyana Molokanova, Sosnovskaya now needs a medical exam. Following the incident, “Agora” human rights organization head Pavel Chikov announced a 100,000-ruble ($1,525) reward for information leading to the identification of the police officer who punched Sosnovskaya.

The attack on Sosnovskaya has inspired public support for the woman from at least two Russian celebrities: the musicians Egor Kreed and Sergey Lazarev. Kreed asked his Instagram followers to send him any information about the officer’s identity, writing, “I’ve already personally submitted a request, and they promised to find him!” Lazarev called the officer’s actions “inhuman,” and wrote on Instagram: “I’d like to see his face! It’s a damned shame. A disgrace!”

Identifying the officer in question is no simple task. Judging by the video footage, he wasn’t wearing the police badge that all officers are required to display. He was, however, wearing a helmet and face-mask. It’s also unlikely that the officer stated his name to Sosnovskaya, before arresting her.

In late July, activists launched a public campaign to require members of the police and National Guard to wear large badge numbers on their uniforms. A petition demanding these reforms now has more than 125,000 signatures at Change.org.

Update: The police officer who punched Sosnovskaya may have been identified.