IMPERIAL, Mo. — Authorities say two men broke into the suburban St. Louis home of an ex-girlfriend’s father as part of a plot to kill him but instead stole his car.

Eighteen-year-old Casey Duncan, of Arnold, and 19-year-old Jesse Killian, of Cape Girardeau, were charged Tuesday with conspiracy to commit murder, stealing a vehicle and burglary. No attorney is listed for them in online court records. Bond is set at $500,000 for each man.

Police say the investigation began after the car was stolen from the Imperial home of Duncan’s ex-girlfriend’s father. Officers then used the car’s GPS system to track it to a St. Genevieve hospital, where Duncan and Killian were arrested. It wasn’t clear why the men were at the hospital. Police say the homicide plot was uncovered during questioning.