Journalist Pavel Sheremet talks on the air at a radio station in Kiev, Ukraine on October 11, 2015.

© 2016 Reuters

Pavel Sheremet, a leading journalist, was killed in central Kyiv one year ago today when a bomb planted in his car exploded. We still don’t know who did it and why.

Sheremet was known for his incisive journalism, raising issues of public concern – such as violence by volunteer battalions and investigations into corruption – that were often uncomfortable for the authorities. Since the early 1990s he had lived and worked in Belarus, Russia, and Ukraine, and was harassed, threatened, and detained for his work. For the past five years, he had been based in Ukraine, working for Ukrainskaya Pravda, a fiercely independent newspaper, and as a presenter at the Vesti radio station.

Ukraine’s President Petro Poroshenko and Prosecutor General Yuri Lutsenko both promised on several occasions to do everything possible to find Sheremet’s killers. Yet we are no closer to knowing the truth than a year ago. What is clear is that there are many questions about the investigation, and Ukraine’s authorities have yet to provide convincing answers.

A team of journalists and researchers from the “Investigation.Info” project and the International Organized Crime and Corruption Reporting Project conducted their own investigation into Sheremet’s murder, revealing their findings in documentary “Killing Pavel.” They exposed major gaps in the official investigation, including the failure to identify and question several witnesses present at the crime scene before and during his car’s explosion. Investigators also disregarded key surveillance footage as evidence. A July report by the Committee to Protect Journalists also revealed glaring shortcomings in the authorities’ probe into the killing. All this poses questions about the authorities’ ability and willingness to conduct a rigorous and effective investigation.

Yesterday, several dozen prominent Ukrainian human rights defenders and journalists, along with international groups, published a joint open letter to the country’s leadership demanding an effective investigation into Sheremet’s death, calling for true transparency about its progress. Ukrainian authorities cannot afford to ignore these calls for justice. They need to go beyond unmet promises to deliver justice and answer the question: Who killed Sheremet?