A week after the murder of human rights activist Natalya Estemirova, a Russian rights group has disclosed the death of one of its members who had gone missing in May, news media reported Thursday, according to dpa. The group Spravedlivost (Justice) a local human rights organization, disclosed that the body of the group's leader, Andrei Kulagin, had been found on July 10 in a sand quarry near the city of Petrazavodsk in Karelia, a republic which borders with Finland. It remained unclear why the group had delayed so long informing the media of the discovery of the body. Police have only confirmed the death of Kulagin. Kulagin's colleagues suspected that Kulagin was killed in connection with his advocacy of more humane prison conditions, the radio station Ekho Moskvy reported. Kulagin had been missing since May 14. He had left his house late at night for a previously agreed-upon meeting, the news agency Ria Novosti reported. A taxi driver testified later that he had brought Kulagin to a cafe. The police reported on Wednesday that they did not know of the victim's work as a human rights activist. Kulagin had previously been convicted for hooliganism, among other crimes, they said. According to news agency Interfax, another human rights organization in Petrozavodsk described Kulagin as a businessman who supported prison reform. The murder in mid-July of human rights activist Natalya Estemirova provoked dismay abroad as well as in Russia. Like Anna Politkovskaya, a journalist killed in 2006, Estemirova had investigated crimes committed against Chechen civilians. Critics of the Russian government fear that in the case of Estemirova, the person who ordered the killing as well as the killer will go unpunished, as has been the case in the deaths of other human rights activists in Russia. In the Politskovskaya murder case, a Moscow court last February acquitted four suspects. But in late June, Russia's Supreme Court overthrew that verdict and ordered a re-trial, which is set to start on August 5.