Prime Minister David Cameron reacted to the "truly shocking events" in Shipley, telling MPs at PMQs: "We must make sure that justice is done."
These were truly shocking events and reading about them this morning, particularly the young boy who staggered out of the park bleeding, having been stabbed, and the grandmother who was described as someone who was so much a community member that they were seen as everybody's grandmother, is truly disturbing.
A 26-year-old man remains in custody after he was arrested on suspicion of the murder of 84-year-old Louisa Denby, who he is related to, and the attempted murder of a nine-year-old boy who was stabbed in a skate park, police said.
A second 26-year-old man was also arrested in connection with Mrs Denby's murder, while three men aged 18, 24 and 29 were held on suspicion of attempted murder over the incident in the skate park.
All four have been released without charge, police said.
A nine-year-old boy remains in hospital as detectives investigate links between his stabbing, the murder of a retired teacher and an incident in which an eight-year-old girl was chased through a garden.
A 26-year-old man has been arrested on suspicion of the murder of an 84-year-old woman and the attempted murder of a nine-year-old boy who was stabbed in a skate park, police said.
Officers found the pensioner's body in a bedroom at her home in Prospect Mount, Shipley, West Yorkshire, after reports that the boy had been attacked in the Carnegie skate park in the town.
West Yorkshire Police named the dead woman as Louisa Denby and said she had suffered "numerous stab wounds".
The man was arrested at 4.10am this morning in nearby Idle on suspicion of murder and attempted murder, a West Yorkshire Police spokesman said.
Another 26-year-old man has also been arrested on suspicion of murder and three other local men have been arrested over the incident in the skate park, the spokesman added. The boy was taken to Leeds General Infirmary where he remains in a stable condition, police said.
A 26-year-old man was arrested on suspicion of the murder of an 84-year-old woman whose body was found in a house in Shipley and the non-fatal stabbing of a nine-year-old boy in a skate park, also in Shipley, West Yorkshire Police said.