An envelope taped to the front door of Mayor Jayne Peters' home contained a key to the house and a typed note advising police they would discover something unpleasant inside, Coppell Deputy Police Chief Steve Thomas said.

Three other notes contained instructions for handling affairs, such as taking care of the family dogs, but did not provide explanations for the deaths of the 55-year-old Peters and her 19-year-old daughter, Corinne.

"It appeared to me that there had been some thought," Thomas said.

Police found the bodies Tuesday after the mayor failed to show up at a city council meeting. They said the Dallas County Medical Examiner's Office ruled Wednesday that the case should be officially classified as a homicide-suicide investigation.

"Forensic tests (and) procedures performed point to Corinne being the victim in this tragedy, with Mayor Peters subsequently taking her own life," police said in a statement. "Both of the fatal injuries are a result of a single gun shot wounds."

Thomas said the weapon was a semiautomatic handgun and there were no signs of a struggle.