The 48-year-old man used a flame-thrower he had created from a propane gas container to set the elderly couple alight as they lay in bed late Friday, chief police investigator Anton Kiesl said.
The woman burned to death in her bed, while her husband's body was found on a bench outside their home in the southeastern village of St. Magdalena am Lemberg, Kiesl said.
Both victims were in their 80s; the woman's lower legs had been amputated due to diabetes-related complications.
The man's motive was not immediately clear. His wife - and the victims' daughter - was in the house at the time of the incident, and escaped through a window, Kiesl said.
The chief investigator said the man fled the scene and stabbed himself in the stomach. The man, who was not identified by name, is now in an induced coma following an emergency operation.