Her husband was away on a business trip at the time.
Galina Ryabkova, who is seen on surveillance video shortly after the incident, appeared emotionless after going to look at the remains of her sons, ages 4 and 7, according news reports.
The video - posted by the tabloid LifeNews.ru - begins with one of the children landing just out of frame at the bottom of a short flight of steps outside the building. A man is then seen coming out to discover the gory scene, a major newspaper reported.
Ryabkova also comes downstairs, the video shows. Wearing a white t-shirt and jeans, she sits in the lobby as neighbors attempt to keep the bony blonde from walking away.
“My wife woke me up and said that there were children falling out," a neighbor told a TV news channel.
“We ran out and saw two children lying on the ground in front of the main door. Just at that time their mother was leaving the building. We asked her if these were her children and she replied, emotionlessly, ‘Yes, I threw them away’,” he said.
Authorities can be seen at the end of the video covering up the bodies with a white blanket, then entering the building.
The authorities said that the 30-year-old woman and her family lived on the 8th floor of the apartment building, but she took the children up to the 15th before tossing them off.
The woman initially told authorities her boys were now “angels in heaven,” before refusing to talk, Sergey Markin, the Investigative Committee spokesperson, told RIA Novosti.
However, it is still unclear why Ryabkova, who reportedly had tried to commit suicide in the past, killed her two children.
Ryabkova is expected to be sent to a psychiatric hospital for evaluation and if convicted, could spend the rest of her life in prison.