PCs Nicola Hughes and Fiona Bone (PA)
ACC Shewin also disclosed that a 22-year-old man had been arrested for setting up a tribute page on Facebook to Dale Cregan, who is being questioned over the murders.
The page was entitled "Dale Cregan is a hero".
He said: "Anybody who perhaps wishes to take the opportunity following such a tragedy to tastelessly add derogatory comments and perhaps think that they are poking fun at such at such a tragic situation will always cause a great degree of emotion.
"Not just in police officers but ordinary members of the public. I looked at some of these websites and saw ordinary members of the public alarmed and really distressed at some of the ridiculous comments put on there.
"And I think they would have wanted us to be able to take positive action and that's exactly what ourselves and Merseyside Police have done."
The parents of PC Nicola Hughes will today pay their respects to their "beautiful" daughter after she was killed as she responded to a hoax burglary call.
Natalie Hughes, Nicola's stepmother, said it has been "incredibly hard" for the family as they struggle to come to terms with their daughter's death.
Today, they will view Nicola's body for the first time since she was killed in a gun and a grenade attack as she approached a property in Hattersley, Greater Manchester.
In a message posted last night on Facebook, she said: "Today has been an incredibly hard day for us all, but I am so proud of my wonderful husband Bryn Hughes, my fantastic step-son Sam Hughes, his girlfriend Natalie Hughes and Nicolas [sic] boyfriend Gareth Cleminson.
"I love you all and we will be strong together when we see our beautiful Nicola tomorrow".
Theresa May, the Home Secretary, was given a two hour briefing on the killings after travelling to Greater Manchester yesterday.
She rejected calls to arm the police, and paid tribute to the "brave and talented" officers who were killed.
She said: "The murders of PC Fiona Bone and PC Nicola Hughes were acts of savage brutality. They have left grieving families and devastated Greater Manchester Police force.
"These were brave and talented officers who were going about their everyday duties, doing what they do, day in, day out, protecting the public, fighting crime and they were incredibly brave and their deaths are a reminder of what police officers face every day."
Shadow home secretary Yvette Cooper pays tribute to PC Fiona Bone and Pc Nicola Hughes
Police are today continuing to search for more hand grenades amid growing concerns that they are in the hands of criminal gangs.
Sir Peter Fahy, chief constable of Greater Manchester Police, yesterday told officers that feuding criminals may possess more of the weapons and could be preparing to use them against the police.
The attack on Pcs Fiona Bone and Nicola Hughes, who were killed as they responded to a hoax burglary call on Tuesday morning, was the fourth in Manchester in little over a month in which grenades were used.
At a news conference, Sir Peter said: "We are not confident that we have recovered all the grenades; we don't know for certain, so we've made it clear to our officers that the threat is still there.
"I would want that to be the message, this has been a long-standing criminal feud between different outfits in Manchester and in the Tameside area, and that threat is very much there."
Police believe that the grenades are former military weapons that arrived in a shipment from the former Yugoslavia. It is thought that at least eight are still on the streets of the city.
Further details emerged last night about the attack on the two officers, with one witness claiming that Pc Bone, 32, had her police-issue Taser stun gun in her hand when she was shot.
Pc Hughes, 23, is believed to have attempted to run off to escape the gunman but had a grenade thrown at her before she too was shot.
She was seen lying in the road muttering for help, but died in hospital.
One witness said: "I heard a bang that shook the house so I ran out and saw a woman on the floor who I could tell was already dead; there was blood all over her.
"It looked like she had been in a boxing ring. She had a Taser in her hand and she was lying by the window of the house. I think that the younger officer tried to run away because she was further away from the house. She was lying there muttering for help."
Police confirmed last night that the gun used in the attack had been recovered.
As colleagues of the two officers held a minute's silence yesterday, police continued to question Dale Cregan, 29, on suspicion of their murders.
Police disclosed that they had also arrested a 28-year-old man on suspicion of conspiracy to commit murder.
Cregan was also being questioned on suspicion of the separate murders of David and Mark Short, a father and son, earlier this year. Mark, 23, was shot in the neck while drinking in the Cotton Tree pub in Droylsden, Greater Manchester, on May 25. Cregan was arrested at the time on suspicion of that murder, but was bailed pending further inquiries because there was not enough evidence to charge him.
On Aug 10, Cregan was again a suspect after David Short, 46, was shot on the driveway of his home in Clayton, Greater Manchester. His assailant threw a grenade under his body as he lay dying. Nine minutes after that murder, two men were seen on CCTV carrying out a grenade attack on a house three miles away.
Officers later found a white Vauxhall van close to the scene which bore the hallmarks of a grenade explosion inside.
It was not clear whether the vehicle had been booby trapped or if a grena
de had gone off accidentally.
The attacks were thought to be the first in which hand grenades were used by criminal gangs on mainland Britain.
Patrick Mercer, the Conservative MP and former Army officer, said: "These grenades are readily available on the black market and easy to conceal on your person and use.
"We are seeing a move from explosives being used by terrorists to being used by criminal gangs, which is extremely alarming. It introduces a completely different dimension into protection for police officers. What would concern me is if this starts to be copied by other gangs and individuals."
Sources claimed that Cregan was acting with the help of about a dozen supporters while he was on the run.
Sir Peter stressed that his force's main priority was to support the dead officers' families. "I would like to say how impressed we've been by the dignity of these families. Both have said how proud they were of Nicola and Fiona, and how proud those two officers were to serve the public. Both families have separately said that their loved ones died doing the jobs they loved," he said.
