James Redmond, with an address at Killinarden Estate, Tallaght, Dublin 24, was charged with murdering Mary Dargan and attempting to murder Karina Dargan at their home in Killinarden Estate on March 15, 2014.
Mr Redmond pleaded not guilty by reason of insanity to the two charges at the Central Criminal Court.
Pauline Walley, prosecuting, told the jury that both families were neighbours and had lived “peacefully and amicably side by side” in the Killinarden Estate for many years.
Mr Redmond had become depressed some months earlier and he wrongly believed Karina Dargan was “chanting” that he was a paedophile and it was being said about him in the community.
It was established during the trial that there was “no substance or truth” to these allegations nor any basis in reality for them.
On March 15, Mr Redmond left his home, jumped over the back wall with a shotgun and shot Mary Dargan dead.
Her daughter Karina was also shot in the head but survived.
Two consultant forensic psychiatrists gave evidence that Mr Redmond was suffering from “severe depressive episodes with psychotic symptoms” and would have been unable to refrain from his actions.
They both said that he met the requirements for the special verdict of not guilty by reason of insanity.
Yesterday a jury returned majority verdicts of not guilty on both counts.
Mr Justice Eagar then made an order committing Mr Redmond to the Central Mental Hospital and to be brought back before the court at 9am today.
Brendan Grehan, defending, told the court he had been asked by his client to say he was “as sorry as any person can ever be” for his “terrible actions” and the “devastating consequences for the entire Dargan family”.
Ms Walley then read two victim impact statements. The first was on behalf of the six Dargan children.
“It is hard to communicate in words how the brutal destruction of our family’s way of living would be torn apart in the most senseless of ways,” they said.
“The loss of our guiding light and the struggle for justice has brought us to our knees in heartbroken disbelief. We are crushed and empty,” they said.
The second victim impact statement was on behalf of Karina Dargan. She said that on March 15, 2014, her life was “ruined and destroyed forever” after witnessing her mother being killed.