Boris Nemtsov's girlfriend, Anna Duritskaya, who was with him at the moment he was shot, has returned to her native Ukraine, Russia's Investigative Committee said Tuesday.
In a statement published online Tuesday, the body in charge of the investigation said Duritskaya had already given evidence and undertook to continue to cooperate with investigators.
Investigators said they are actively working to track down Nemtsov's killers, adding they had obtained closed-circuit television footage from the scene, and scheduled ballistic and medical tests.
The Committee said the killing was painstakingly planned and that the organizers knew in advance where Nemtsov would be.
Material from the Moscow Times was added to this report.