Greater Manchester Chief Constable Sir Peter Fahy laid flowers at the scene where two police officers were killed and said he anticipated "developments" in the next 24 hours over possible charges relating to their deaths.
PC Nicola Hughes, 23, and PC Fiona Bone, 32, were killed in a gun and grenade in Hattersley, Greater Manchester, on Tuesday morning.
One of the country's most wanted men, Dale Cregan, 29, handed himself in to the police shortly after the attack.
A warrant of further detention was obtained last night for Cregan which will expire at 9am tomorrow.
The second man arrested in connection with the killings of two police officers was named tonight as 28-year-old Stephen Garvey.
Garvey was arrested on suspicion of conspiracy to commit murder.
Sir Peter also paid tribute to the constables, calling them "two wonderful human beings, two very dedicated officers".
He said the families of the victims were "overwhelmed" by the "massive show of public support" in the wake of their deaths.
A 28-year-old man, who was arrested yesterday in Hattersley on suspicion of conspiracy to commit murder, also remains in police custody.
Earlier, Assistant chief constable Garry Shewan said the criminal feud which preceded the two murders had "to end" and that "enough is enough".
He added that the killings of Miss Hughes and Miss Bone, were a "watershed moment".
ITV News' Midlands Correspondent, Rupert Evelyn reports from Hattersley.
Mr Shewan also confirmed that a 22-year-old man from Mersey had been arrested over an offensive Facebook page created after the PCs deaths.
Earlier, the country's top prosecutor, Keir Starmer QC, said "the time has come for an informed debate about the boundaries of free speech in an age of social media".
Police have been given more time to question 29-year-old Dale Cregan on suspicion of the murders of PC Fiona Bone and PC Nicola Hughes.
A warrant of further detention was obtained on Wednesday night and is due to expire at 9am on Friday morning.
A 28-year-old man who was arrested on suspicion of conspiracy to commit murder yesterday also remains in police custody