Four men and a woman arrested in London over the killing of Pc Sharon Beshenivsky in Bradford have arrived in West Yorkshire for questioning.
A police convoy brought those being questioned to West Yorkshire
They were arrested on Saturday after the shooting outside a travel agents in Bradford on Friday.
The five were driven from the capital under armed guard along the M1, in a convoy of seven police vans. One man remains in custody in London.
Pc Teresa Milburn, who was also shot in the attack, left hospital on Sunday.
She appeared on the steps of Bradford Royal Infirmary in a wheelchair pushed by her husband, Christopher, and flanked by armed police.
The officer, who was carrying flowers and a pink cuddly toy, began crying as she was led away from the hospital.
Pc Beshenivsky had three children and two step-children
The Bishop of Bradford, the Rt Rev David James, said the tragedy had united the community.
"This tragic killing has brought people of Bradford together in support of the family of the murdered police woman and her colleagues," he said.
Meanwhile, former Met Police chief Lord Stevens called for the death penalty for those who murder police officers.
'Doing her job'
And Pc Beshenivsky's father, Billy Jagger, said he wanted to kill his daughter's murderer "with my own bare hands".
He told the News of the World: "She was and always will be a one-in-a-million daddy's girl. I'm dying inside thinking of life without her.
"She was only trying to do a job and now her life has been taken away."
Pc Milburn was discharged from hospital on Sunday afternoon
Pc Beshenivsky, 38, had been a police community support officer for two years before becoming a police constable in February 2005.
She had three children and two step-children and lived in a converted barn in Keighley, West Yorkshire.
Pc Milburn, 37, who comes from a large family in the Bradford area, had previously been a machinist and was hoping for a "complete change" and "new opportunities" in joining the force.
The shootings have raised calls for police to be better equipped or even routinely armed.
Pc Beshenivsky had been wearing body armour which gave limited ballistics protection.
However, Tom McGhie, chairman of the West Yorkshire Police Federation, said: "There are types of body armour which offer a much higher level of ballistic protection but the problem is they would be almost unwearable."
And Home Office minister Hazel Blears rejected calls for the police to be routinely armed.
"It is important that the police have a very close relationship with the public and for them to routinely carry guns might put that relationship at risk," she said.