A 26-year-old man who murdered his 84-year-old grandmother and attempted to murder a nine-year-old boy will be sentenced today.
Nathaniel Flynn has admitted killing Louisa Denby at their home in Shipley, West Yorkshire, in July, and stabbing Jason D'Arcy in a nearby skate park.
Police said retired teacher Mrs Denby was subjected to a brutal and frenzied attack at the hands of Flynn who has never explained why he killed her.
After stabbing his grandmother to death, Flynn then targeted and attacked nine-year-old Jason as he played near his home.
Detectives said it was " only through sheer luck that he wasn't murdered".
Flynn, of Prospect Mount, Shipley, then tried to entice an eight-year-old girl from her garden where she was playing and later assaulted a 59-year-old man outside his home.
He was due to go on trial earlier this month but pleaded guilty to charges of murder and attempted murder.
After the last hearing, Detective Chief Inspector Nick Wallen of West Yorkshire Police said: "Louisa Denby was subjected to a brutal and frenzied attack at the hands of her grandson Nathaniel Flynn.
"To this day we still have no idea why he attacked her. Louisa was a lady, adored by her family, who had only ever shown her grandson love and kindness."
Mr Wallen said: " He's killed an elderly defenceless lady and he's tried to kill a nine-year-old boy who was young, defenceless and in an area where he felt safe - a comfortable place where he was playing like any nine-year-old child would."
The detective added: "I simply can't explain why he did what he did.
"To this day Mr Flynn has never given us any account of why he did these terrible things to his grandmother and to nine-year-old Jason D'Arcy. We have no idea why he did these terrible things."
He said Flynn spent the day between attacks wandering around the local area and hiding in the surrounding countryside. The officer said he was tracked down partly due to an outpouring of public help using a range of social media.
Mr Wallen said Jason was hit in the arm but was almost certainly defending himself from a blow aimed at his chest.
Flynn will be sentenced at Bradford Crown Court .