Investigators work at the place where Lt. General Igor Kirillov, the head of Russia's Nuclear, Biological, and Chemical Defence Forces and his assistant, seen at lower center, were killed by an explosive device planted close to a residential apartment's block in Moscow, Russia, Tuesday, Dec. 17, 2024. (AP Photo)

EDS NOTE: GRAPHIC CONTENT - Investigators work at the place where Lt. General Igor Kirillov, the head of Russia's Nuclear, Biological, and Chemical Defence Forces and his assistant Ilya Polikarpov were killed by an explosive device planted close to a residential apartment's block in Moscow, Russia, Tuesday, Dec. 17, 2024. (AP Photo)

Workers load a body of Lt. General Igor Kirillov, the head of Russia's Nuclear, Biological, and Chemical Defence Forces into a bus after he and his assistant Ilya Polikarpov were killed by an explosive device planted close to a residential apartment's block in Moscow, Russia, Tuesday, Dec. 17, 2024. (AP Photo)

Investigators work near a scooter at the place where Lt. General Igor Kirillov, the head of Russia's Nuclear, Biological, and Chemical Defence Forces and his assistant Ilya Polikarpov were killed by an explosive device planted close to a residential apartment's block in Moscow, Russia, Tuesday, Dec. 17, 2024. (AP Photo)

FILE - In this photo taken from video released by Russian Defense Ministry Press Service on Feb. 28, 2023, the head of the radiation, chemical and biological defense troops of the Russian Armed Forces Lt. Gen. Igor Kirillov speaks during a briefing in Moscow, Russia. (Russian Defense Ministry Press Service via AP, File)

Investigators work near a scooter at the place where Lt. General Igor Kirillov, the head of Russia's Nuclear, Biological, and Chemical Defence Forces and his assistant Ilya Polikarpov were killed by an explosive device planted close to a residential apartment's block in Moscow, Russia, Tuesday, Dec. 17, 2024. (AP Photo)