The State Bureau of Investigation is considering four possible theories relating to the death of Major Hennadii Chastiakov on Nov. 6, the law enforcement agency's communications adviser Tetiana Sapian said on air on Nov. 8.
Chastiakov, an assistant to Ukraine's Commander-in-Chief Valerii Zaluzhnyi, was killed on his birthday when a grenade he had been gifted exploded in his home in Chaiky, a suburb of Kyiv. His thirteen-year-old son was seriously injured in the explosion.
Investigators believe that the most likely version of events is that death was accidental, caused by "the careless handling of ammunition," Sepyan said.
However, three other theories are being considered at this stage of the investigation, including a case of murder, a killing organized by Russian special services, and an attempted Russian assassination of a different member of Zaluzhnyi's team.
Interior Ministry spokesperson Mariana Reva also said on Nov. 7 that the explosion was likely the result of careless handling of ammunition.
An unnamed man had confessed to giving Chastiakov the grenade but also said that he had warned him that it was live.
Chastiakov likely disregarded the warning, Reva told RFE/RL's Ukrainian service, and the grenade exploded.
According to the State Bureau of Investigation, the case involves article 410-4 of Ukraine's Criminal Code, which covers stealing, misappropriation, and extortion of weapons and other military equipment committed by a service member under martial law.