A mum set the table for breakfast before she "calmly" drugged and smothered her five children after the split from her husband left her feeling "overwhelmed," prosecutors have claimed.
The children, aged between one and eight, were all found dead by police at a flat in Solingen, western Germany.
All of the kids were discovered lying on their beds, with breakfast dishes still on the kitchen table.
Toxicology reports indicated they were suffocated after being sedated with an “unknown” drug.
The mum, identified only as Christine K, then reportedly texted her mum and said "send the police to the apartment, the children are dead,” before travelling to Dusseldorf with her oldest son, Marcel, 11.
Marcel was left on the train as his mum got off at Dusseldorf Central Station and threw herself onto the tracks.
The boy is reported to have stayed on the train until he reached Mönchengladbach, where his grandmother lives.
Police have said the child was not harmed and is currently in the care of relatives.
They have not questioned him as their "first priority" is helping him.
Chief Investigator Marcel Maierhofer said Christine K is believed to have "carried out the act while she was feeling emotionally overwhelmed, and that too is the motive."
Police believe she became distressed after splitting from her third husband one year ago and suffered deteriorating mental health, reports Bild.
Officers who entered the flat on Thursday are reported to have broken down in tears, a resident told Pledge Times.
Despite being traumatised by what they found, rescuers tried to resuscitate the five children, who were "lifeless."
Police were also reportedly shocked at the state of the flat, and pictures from the scene who handprints on grubby winds and dead plants inside the home.
Social services in Solingen have confirmed the family was known to them, but hadn’t noticed any problems that were cause for alarm.
Christine K was rescued by firefighters, but she remains in hospital seriously injured and detectives will try to interview her once she has recovered.
Police have informed all of the children’s dads, four of whom were from the mum's most recent marriage and two from an earlier relationship.
Stefan Weiand, a police spokesman, said: "We are assuming a crime was committed. How and why that happened, we cannot say.
"At the moment, we assume that the 27-year-old mother was responsible.
"The mother threw herself in front of a train in Dusseldorf and is badly injured.