CATHEDRAL CITY, Calif. -

Investigators on scene of a double murder-suicide in Cathedral City left neighbors on Northhampton Avenue on edge Wednesday.

Police discovered a handgun beside the shooter in the home and a written letter confessing to the killings.

"The mother and daughter were both shot and killed in bed by the male, who then at some point turned the gun on himself and committed suicide," said Lt. Chuck Robinson, of the Cathedral City Police Department.

Police say the man found dead in another bedroom in the house, which he shared with the elder woman, was the mother's common-law husband. He reportedly shot the woman in the head, killed her middle-aged daughter and then shot himself.

Authorities first got the call from the mother's adult son around 11:20 a.m. The son reportedly was checking on his family at the home on Wednesday morning, worried when he couldn't get a hold of them.

"It appeared everybody was asleep in bed. So he didn't wake anybody up, he basically left, then he came back later in the morning to make contact and that's when he found them in their condition," said Robinson.

Family members tell police the daughter, from Florida, was visiting her sick mother who had only months left to live. They say her illness stirred up a fight over her finances.

"Apparently there was some kind of a dispute over end-of-life financial arrangements. We unfortunately think it led to this tragic incident," said Robinson.

Robinson tells us these are the first reported homicides the city has dealt with in more than a year.

"You can't foresee this kind of stuff. This is the definition of a tragedy. This affects so many people," he said.

Neighbors, including Jeremy Sieben, say the community is generally “quiet, no problems of any sort. This is the biggest thing I've seen ever since I've been here," he said.

"It's tough on everybody. It's tough on the family. It's tough on the officers, especially this time of year," said Robinson.

The Riverside County Coroner was expected to conduct autopsies Thursday morning. The names of the dead have not been released.