The 38-year-old man attacked his 37-year-old former lover and her 15-year-old son with a knife, and then fled to a nearby wood where he tried to take his own life.
“It was a tragic and dramatic incident. We've no idea what his motive was,” said the head of the Criminal Investigation Department, Gottlieb Türk.
The man climbed onto the balcony of the apartment at around 2:30 am. The woman heard a noise and when she opened the balcony door he stabbed her. Her 15-year-old son heard her screams and rushed to help her and was also stabbed.
Their attacker then ran off, leaving them to call the police and an ambulance which took them both to hospital in Klagenfurt.
Police search patrols and a helicopter went after the fugitive and found him trying to kill himself by inhaling exhaust fumes from his car in a nearby wood.
He is being treated in hospital and police have said they plan to question him on Saturday. They will also try and find out if he was mentally disturbed at the time of the attack.
The woman and her son were not seriously injured and were able to leave hospital on Thursday morning.