A bomb hidden in an electric scooter killed Lieutenant General Igor Kirillov, a senior Russian official in charge of nuclear protection forces, in Moscow on Tuesday, Russia’s investigative committee announced.

Kirillov, who was the chief of Russia’s Nuclear, Biological and Chemical Protection Troops, was killed outside an apartment building located approximately 7 km (4 miles) southeast of the Kremlin. His assistant was also killed in the explosion.

“Igor Kirillov, the head of the radiation, chemical and biological protection forces of the armed forces of the Russian Federation, and his assistant were killed,” the investigative committee said in a statement.

Photographs shared on Russian Telegram channels depicted a shattered building entrance with debris scattered around and two bodies lying in blood-stained snow.

A criminal case has been opened to investigate the incident.

Russia’s radioactive, chemical, and biological defence forces, known as RKhBZ, are special troops trained to operate in conditions involving radioactive, chemical, or biological contamination.