MOSCOW, Russia — A gunman with a swastika on his teeshirt killed 13 people, including seven children, and wounded at least 21 at a school in Russia on Monday before dying by suicide, investigators said.

The identity of the attacker and the motive for the shooting in Izhevsk, about 600 miles east of Moscow, were not clear.

Russia’s Investigative Committee, which handles major crimes, said the gunman was wearing a balaclava. It released a short video showing his body lying on the floor of a classroom with overturned furniture and papers strewn on the floor. He was dressed all in black, with a red swastika in a circle drawn on his teeshirt.

The committee said the six adult victims included teachers and security guards. It said 21 people, including 14 children, were wounded.