Shotgun wounds to the head caused the deaths of a couple found dead at their home near Loddington earlier this week.
The bodies of Donald, 78, and Margaret Knight, 77, were found at the remote home between Loddington and Mawsley at about 2.10pm on Wednesday, May 1.
The results of the post-mortem examinations have been revealed by police.
A spokesman for Northamptonshire Police said: “Following the deaths of Donald and Margaret Knight on Wednesday, May 1, a forensic post-mortem examination took place last night at Leicester Royal Infirmary.
“The cause of death in both instances has been confirmed as a gunshot wound to the head.”
Det Chief Insp Mark Behan said: “I know that this tragic incident has shocked people in the local community and would like to offer reassurance that we are not seeking anyone else in connection with it.
“My thoughts and condolences are with the family at this difficult time.”
Mr Knight was the former chairman of Kettering lorry firm Knights of Old.
On Thursday the couple’s two daughters released a statement saying they had been ‘devastated’ by the deaths of their parents.
Police say the next step of the investigation will be to open an inquest, although a date for this has not yet been set.