KIEV, May 10 - A former agent of the Ukrainian security service SBU appears to have been engaged in overnight surveillance of a street when a car bomb was planted to kill a prominent journalist in July 2016.

Pavel Sheremet was driving to work when his car exploded. The murder was the most high-profile assassination of a reporter in the country since the beheading in 2000 of investigative reporter Georgiy Gongadze.

A new documentary released by a team of investigative journalists on Wednesday identified the agent as Igor Ustimenko.

Ustimenko admitted being in the area that night and said he had been hired as a private investigator to keep watch on someone’s children. He denied seeing bombers and said police had not contacted him.

Olena Hitlianska, a spokesperson for the SBU, said Ustimenko was dismissed from the service on April 29, 2014, or two months after former President Viktor Yanukovych had fled to Russia after a popular uprising. She did not say why Ustimenko was dismissed.

SBU and other law enforcement agencies have been reshuffled after the uprising, replacing people that were known to be loyal to Yanukovych or supporting pro-Russian policies.

The film, Killing Pavel, suggests that Ustimenko was present when the explosive device was hidden under the journalist’s car, The Guardian reported.

The Organized Crime and Corruption Reporting Project (OCCRP) and Slidstvo.info released the documentary on Wednesday, when it was screened on Ukrainian TV.

The murder of Sheremet is investigated by police. But not much progress has been reported over the past 10 months.

Investigators said Sheremet was killed by a remotely detonated explosive device, most likely in retribution for his investigative work in Ukraine and other places. The journalist supported the pro-western uprising in 2014 that saw Viktor Yanukovych flee to Russia, but had also been bitingly critical of Ukraine’s new authorities.

Surveillance camera footage published by the media and police revealed that an unknown man and a woman approached Sheremet’s Subaru car on the street the night before the blast. The woman is seen kneeling beside the parked car on the driver’s side.

The makers of Killing Pavel tracked down new surveillance footage not found by police. It gives fresh details of the apparent killers, who returned to the scene the next morning shortly before Sheremet got into his doomed vehicle.

The footage reveals several suspicious men who arrived in the street that night. They appeared to be carrying out surveillance. They were still there when the man and the woman went past and allegedly fixed the bomb. The Bellingcat citizen journalist group managed to identify their car – a grey Skoda – and its registration.

The investigative reporters subsequently tracked down one of the men and identified him as Ustimenko.

Sheremet made it only a few hundred feet down Ivan Franko Street when the explosion ripped through his car, mortally wounding him. An ambulance had already taken him away by the time Prytula arrived and recognized the charred hulk of their vehicle.

The killing caused a major scandal, and American FBI specialists were brought in to help identify the explosives. The United Nations deputy high commissioner for human rights, Kate Gilmore, said Sheremet’s murder would be a “test of the ability and willingness of Ukraine’s institutions to investigate assaults on media freedom.”

Ukraine’s president, Petro Poroshenko, had said it was a “matter of honor” that Sheremet’s case be promptly solved. He called for a transparent investigation by police and the security services. (gu/nr/ez)