She killed her sick 10-month-old son by cutting his throat.
The gruesome incident happened while Katharina Katit-Stäheli, 40, was under police custody in a hospital in Spain on Wednesday night, the New York Daily News reported.
She then tried to kill herself by slashing her throat, but she survived. She underwent emergency surgery.
She was on the run from Switzerland after little Dylan Katit was removed from her custody in Zurich. The doctors had discovered that he was suffering from a build-up of fluid in the brain.
She then allegedly kidnapped him as he was receiving vital treatment, on Christmas Eve.
The pair disappeared, but the Swiss police speculated that she would have fled to Spain.
They appealed to Spain's national police for help. They put up posters and urged the people to come up with information regarding the woman and the baby.
On Wednesday afternoon, law enforcement officials were called to the Carrefour supermarket in Torrevieja, in south-eastern Spain, after being told of a possible sighting. The police then arrested and transferred them to a hospital so that the son could receive treatment.
A Spanish police spokesman told AFP: "She (the mother) said she was going to bathe him or change his diaper. She took advantage of that moment to kill him.
Get The New Paper for more stories.