Manchester police killings: Dale Cregan was on bail. PC Fiona Bone and PC Nicola Hughes were killed in the attack Police believe PCs Fiona Bone and Nicola Hughes were deliberately "drawn" to the scene Related Stories. A man suspected of killing two female PCs in Greater Manchester was on bail over a fatal pub shooting, police have confirmed. PCs Nicola Hughes, 23, and Fiona Bone, 32, were killed in a gun and grenade attack after apparently being lured by a hoax burglary report. Dale Cregan is being held on suspicion of their murders and two others. In June, Mr Cregan, 29, was questioned over the shooting of Mark Short in a Manchester pub and released on bail. Detectives are continuing to question Mr Cregan over the deaths of PCs Hughes and Bone. The police constables had been sent to investigate what appeared to be a routine burglary report in Abbey Gardens, Mottram, when they were attacked with a gun and a grenade.Death penalty call Greater Manchester Police said it appeared they had been deliberately "drawn" to the scene. In a statement, Chief Constable Sir Peter Fahy said there was insufficient evidence available to charge Mr Cregan over the pub shooting and he had to be released. Mark Short, 23, was shot dead at the Cotton Tree pub in Droylsden, Greater Manchester, on 25 May. In June, Mr Cregan was arrested in connection with this death. Floral tribute Floral tributes to the police officers have been left at the scene Sir Peter said: "It is absolutely normal in complex crime inquiries that when people are arrested there are occasions where there is insufficient evidence available for them to be charged. "In those circumstances suspects have to be released on bail as there are strict time limits covering how long suspects can be held in custody without charge. "That is exactly what happened in this case." Miss Bone's father Paul has called for the death penalty for anyone convicted of murdering a police officer. A witness at the scene where the PCs were attacked in Tameside on Tuesday reported hearing 13 gunshots and an explosion shortly before 11:00 BST. One of the officers died at the scene and the second was critically injured and died afterwards. Mr Cregan was detained when he walked into Hyde police station a short time after the incident. Dale Cregan Dale Cregan is now being questioned over four murders Two people from the house, a man and a woman, are helping police with inquiries. Sir Peter said it may have been one of the "darkest days" in the history of the police service. He said the officers exemplified the very best of British policing. He said Miss Bone was a "calm, gentle woman", an "excellent bobby" and had been in the middle of planning her wedding. He paid tribute to Miss Hughes, describing her as a "chatterbox" and a "great bobby" who was "always smiling". The outrage prompted renewed calls for the routine arming of police. But Sir Peter said his force believed "passionately" that police should remain unarmed, despite the tragedy. Ian Hanson, chairman of the Greater Manchester Police Federation, said: "What we've got are two young girls who went out this morning and they've got an absolute right to come home to their loved ones. "This is cold-blooded murder, the slaughter of the innocents." Prime Minister David Cameron said the killings were an "absolutely despicable act of pure evil". Association of Chief Police Officers president Sir Hugh Orde said the deaths were "deeply sad news for the police service". The police flag at Greater Manchester Police headquarters has been lowered to half mast.Huge manhunt The force has also opened a on its website. Mr Cregan had been the subject of a huge manhunt after the murder David Short, 46, Mark Short's father. A £50,000 reward was offered for information leading to his arrest. On 10 August, David Short was killed at his home in Folkestone Road East, Clayton. He was found dead after an explosion was heard. Four men have already been charged in connection with Mark Short's murder and are due to enter pleas at Manchester Crown Court in November. A 33-year-old man and a 24-year-old man have been charged with the murder of David Short. Mr Cregan is now being questioned over the deaths of David and Mark Short, as well as the murders of the two police officers.