Joan Hoggett was fatally stabbed as she worked.
Ethan Mountain attacked the 62-year-old at the One Stop shop on Sea Road, Sunderland, in September 2018.
Mountain, of Heaton Gardens, South Shields, admitted manslaughter with diminished responsibility but denied murdering the grandmother – claiming he was “not in the right frame of mind” at the time of the offence.
In March, a Newcastle Crown Court judge ordered a jury to find Mountain not guilty of one count of murder on the grounds that his mental responsibility for the killing was diminished.
Mountain, who was admitted to a psychiatric hospital in 2017 and treated with antipsychotic medication, was told he would spend an indefinite length of time in a secure hospital.
In court, moving victim impact statements were read from Mrs Hoggett’s traumatised family.
They told of the horror of spending Mrs Hoggett’s birthday in court and seeing the horror-style mask Mountain was wearing during the onslaught – instead of being out celebrating with their loved ones.
Michelle Young, Joan’s daughter, said: “She was the rock that kept the family together and she really was the life and soul of the party.”
And Sarah Brown, Joan’s granddaughter, added: “Ethan Mountain has taken the sharpest tool out of his bag and torn my family into a million pieces.
"He has caused so much heartache. The sadness and anger can’t be put into words.”
Find out more about the Knife Angel here.
