Flowers are attached to the facade of an apartment block in Moscow, Russia, on Wednesday, Dec. 18, 2024, where a bomb killed Lt. Gen. Igor Kirillov, the head of Russia's Radiation, Biological, and Chemical Defense Forces, and his assistant, Ilya Polikarpov. (AP Photo/Dmitry Serebryakov)

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)

A man lays flowers on Wednesday, Dec. 18, 2024, at the apartment block in Moscow, Russia, where a bomb killed Lt. Gen. Igor Kirillov, the head of Russia's Radiation, Biological and Chemical Defense Forces, and his assistant Ilya Polikarpov. (AP Photo/Dmitry Serebryakov)

FILE - Maj. Gen. Igor Kirillov, the chief of the Russian military's radiation, chemical and biological protection unit, attends a briefing in Kubinka Patriot park, outside Moscow, Russia, on June 22, 2018. (AP Photo, File)

A person walks past an apartment block in Moscow, Russia, Wednesday, Dec. 18, 2024, where a bomb killed Lt. Gen. Igor Kirillov, head of Russia's Radiation, Biological and Chemical Defense Forces and his assistant, Ilya Polikarpov. (AP Photo/Dmitry Serebryakov)