Greater Manchester Police fell silent to remember two of their officers who were killed in a grenade and gun attack.
Pcs Nicola Hughes, 23, and Fiona Bone, 32, died on Tuesday after they were called to investigate what appeared to be a routine burglary report.
Fellow officers and civilian staff at GMP held a minute's silence at 11am in memory of the pair.
Thousands of tributes have poured in for the women, and Pc Hughes's family said she had died doing "the job she loved".
Home Secretary Theresa May is due to meet GMP Chief Constable Sir Peter Fahy later - it is understood she has cut short her holiday in the wake of the murders.
Soon after the two policewomen died, one of the country's most wanted men, Dale Cregan, 29, gave himself up to police. Cregan had been questioned and bailed in connection with the murder of Mark Short, 23, who was shot dead in a Manchester pub in May.
Mr Short's father, David Short, 46, who had branded his son's killer "a coward", was murdered in a gun and grenade attack at his home in August. Cregan was wanted for questioning over both killings.
At a press conference on Tuesday, Sir Peter said it was one of the "darkest days" in the history of the force. He told reporters: "Clearly we are devastated today by the loss of two of our officers."
Sir Peter paid tribute to Pc Hughes, describing her as a "chatterbox" and a "great bobby" who was "always smiling". He said Pc Bone was a "calm, gentle woman" and an "excellent bobby".
Police said Pc Bone had been in the middle of planning a civil ceremony for her same-sex partnership.