The police chief who led the investigation into the knife rampage of Nathaniel Flynn told how more people could have been hurt or even killed if he had not been caught.

Senior investigating officer, Detective Chief Inspector Nick Wallen, said it was thanks to the response of the community of Shipley that Flynn was identified and arrested so quickly.

“In the initial stages we had no idea who had committed these offences,” he said.

“The evidence showed Nathaniel Flynn had been laying in what was described as a den close to a children’s nursery.

“We know he went to the garden of an eight-year-old girl, and I believe if he had not been apprehended so quickly we could have had more people attacked.

“I am very grateful that people came together as they did. Policing works at its best when supported by members of the local community, and that support was truly there.”

Det Chief Insp Wallen said the attack on Louisa Denby was “brutal and frenzied”.

He added: “It was a savage and ferocious attack on a defenceless elderly lady, followed by a savage and ferocious attack on a vulnerable nine-year-old boy.

“I cannot recall dealing with anything quite so appalling in my 26-year career.”

He said Louisa Denby was a lovely woman whose family meant everything to her.

“She was a kind, loving woman, supporting her grandson. She was well aware he had problems in life and she was doing her best to support and help him.

“We can only imagine the impact of Flynn’s actions upon her family who continue to suffer from the consequences of her loss to this day.”

Det Chief Insp Wallen said Flynn had a history of drug abuse. But he added: “To use that as an excuse for what he has done would be wholly wrong and inappropriate. I don’t think drug abuse is responsible for what happened.

“He was a difficult individual with a difficult background, living with an elderly woman. He was using drugs. He was probably in pain from fracturing his back in a fall. If you add all that together maybe it’s why he snapped and he ended up taking the actions that he did.”

The officer said Flynn’s relationship with his mother appeared to have broken down, which led to him living with his grandmother in quite unusual circumstances.

Det Chief Insp Wallen commended the courage of Jason D’Arcy, who “suffered a terrifying attack at the hands of Flynn, and yet has shown great strength in recovering so well.”

He said Jason knew the moment he had been stabbed he needed to get home and get help and did not panic. He said: “We are all immensely proud of him and the courage he has shown.”

Det Chief Insp Wallen read a statement on behalf of Jason’s father, Lee D’Arcy, in which he said: “Jason is still recovering from what happened that day, but he is making very good progress and we are hopeful that the support he has been given by everyone will aid him in his recovery.

“We would like to thank our family and friends for their support during what has been a difficult time, along with the emergency services who responded swiftly to the incident.

“We would also like to thank the police officers who have given us great comfort and reassurance with their support and the way they have handled the investigation.”

A statement by Barbara Robinson, Louisa Denby’s daughter and Flynn’s aunt, on behalf of the family, said: “The sudden horrific murder of our mother has had a devastating effect on our family. Now we hope to rebuild our lives, although our mother will never be forgotten.”