A father told his doctor he thought his son had tried to kill him just 24 hours before he was blasted to death with a shotgun, a court heard.
Robert Seddon, 68, survived after his son Stephen allegedly drove a car into a canal with his parents aboard, in a fake road crash designed to kill them for their £230,000 will.
Retired British Airways worker Mr Seddon later confided in his GP he now believed the canal "accident" four months earlier had been a deliberate attempt to kill him, Manchester Crown Court heard.
The next day Stephen Seddon, 46, an "ungrateful son" with an "insatiable thirst" for his father's cash, went to the suburban family home in Sale, Greater Manchester, and shot both parents at close range with a sawn-off shotgun, it is alleged.
Seddon, a father-of-three from Benevente Street, Seaham, County Durham, denies two counts murder on July 4 last year and two counts of attempted murder over the canal incident earlier that year on March 20.
The day before Mr Seddon and his wife Patricia, 65, were shot dead he had an appointment with his GP, the court heard.
"He had previously expressed a view the canal incident was an accident," Peter Wright QC, prosecuting, told the jury. "By this time he was expressing his concerns to his GP that his son had tried to kill himself and his wife when his son drove into the canal." Mr Seddon also told the doctor he was going to confront his son about it.
Mr Seddon and wife Patricia, 65, described as a quiet, unassuming elderly and caring couple, gifted their son £40,000 in cash and bought his home to keep a roof over his head. But they "had to die" because the defendant stood to inherit everything in their wills, the court heard.
After their bodies were discovered police contacted Seddon to tell him his parents had been shot and his reactions were "odd". "He began moaning when he spoke," Mr Wright said. "Not enquiring as to the circumstance of their deaths, but as to his own predicament."
Seddon told officers: "What am I going to do now? I'm going to lose the house, the mortgage is in my Dad's name." Seddon also failed to ask about the welfare of his nephew, the jury heard.