Major Genadi Chastiakov, assistant chief of the army Ukrainian, Valeri Zaluzhni, has died when a grenade he had received from colleagues in the Armed Forces on the occasion of his birthday exploded.

The device exploded in his house, when he was showing it to his family, according to sources from the official investigation of the Ministry of the Interior.

The news of Chastiakoy’s death was announced by the head of the Armed Forces himself, Valeri Zaluzhni, who paid tribute to his subordinate and promised that what happened would be clarified.

“He returned home from work with gifts from his colleagues. He took out a gift box containing several grenades and showed one of the ammunition to his son,” Ukrainian Interior Minister Igor Klimenko explained in a statement, adding that the grenades were “of a new Western model.”

According to Klimenko, Chastiakov’s 13-year-old son began pulling on the ring. Shortly after, he took the grenade and tore off the ring, “causing the tragic explosion.”

The authorities are also investigating the grenades that did not explode and have identified the colleague who gave the gift. “Investigations continue,” Klimenko said. According to Ukrainian media, Chastiakov turned 39 this Monday.