Nuala Kerr, whose son Ronan, 25, died yesterday when a booby-trap bomb exploded as he got into his car in Omagh, Co Tyrone, said everybody was aiming for a neutral police service.
The grieving mother said: "This is at a time when we are striving for a neutral police force for the good of our country and I urge all Catholic members not to be deterred by this. We all need to stand up and be counted and to strive for equality.
"We don't want to go back into the dark days again of fear and terror. We were so proud of Ronan and all that he stood for. Don't let his death be in vain."
Politicians from across the community have urged unity after the suspected dissident republican attack killed the new recruit as he went to work in Enniskillen.
Mrs Kerr said she was also speaking on behalf of his two brothers Cathair and Aaron and loving sister Dairine. Their father Brian died some time ago.
"He was a wonderful son and brother, always had a smile and a helping hand for everyone. He had all the attributes of a great police officer - fair, empathetic, intelligent, humorous, a great communicator and loyal to all who knew him. And he just loved his work," she said.
"I would like to appeal to the wider public for any information, no matter how small about this callous crime. Someone knows something. Would you please come forward and do the right thing so that justice can be done."
She said it was a sad day for the community.
"Ronan was a valued member and he had so much to offer," she added.
The family were being comforted at the family home at Drumduff, near Omagh, this afternoon.
Pc Kerr's brother Aaron was travelling home from Australia for Mother's Day and learned the news on a stopover in the United Arab Emirates when he checked Facebook.
Sinn Fein's deputy First Minister Martin McGuinness branded the murder an attack on the entire community, while his party president Gerry Adams said republican heartlands were "seething with anger" over the "futile" murder.
First Minister Peter Robinson led Stormont colleagues in pledging the attack would not succeed in derailing political progress.
Detectives suspect Mr Kerr had opened the driver's door and was just getting into the car when the bomb fell off the underside and exploded on impact with the ground as he sat down.
Police Federation chairman Terry Spence said: "It won't put off other Catholics and there is clear evidence to support what I am saying.
"If you look at what has happened over the last three or three and a half years there have been a series of gun and bomb attacks on police vehicles and officers.
"The same thing was said on those occasions that people believed Catholics would not join, that did not happen and I don't believe it will happen now."
Mr Spence added: "He was a very caring individual who wanted to be a police officer because he believed he had something to offer the community in Northern Ireland.
"We were thrilled that he had chosen that career but he paid the supreme sacrifice for that."
Chief Constable of the Police Service of Northern Ireland (PSNI) Matt Baggott appealed for the community to move beyond condemnation and help catch the killers - an appeal that was endorsed by political leaders from across the religious divide.
Mr Baggott said he could not imagine what the grieving family was going through.
"A mother has lost her brave son, made all the more horrific that it is Mothers' Day today," he said.
Flanked by Northern Ireland Justice Minister David Ford, he said it was time for communities to put pressure on people he said had only managed to "kill a peacemaker".
"We need these people to be given up. We need these people to be taken out of communities and given up so that justice can be done," he said. "We need good information."
He added: "My emotions are a deep sense of pride in Ronan, and the fact that he chose this career, knowing what the dangers were, that he chose to be a peacemaker and a peacekeeper.
"And he chose to do that absolutely impartially from his community."
Mr Adams endorsed the call for action to ensure this was the last killing of its kind.
He added: "The nationalist and republican people of Tyrone, for example, where this action was carried out, or in west Belfast, heartlands, will be angry," he said.
"This isn't just something which unionists or others will be concerned about. The people who I know, and who I have known all my life, the people I have been in touch with overnight, are seething with anger."
Mr McGuinness, who met the police officer's bereaved family in the aftermath of yesterday's blast, said he had spoken to the policeman's mother, a brother and sister and his grandmother.
"It was a very sad house," said Mr McGuinness.
"Ronan Kerr was someone who appreciated the fact that the environment brought about as a result of the peace process had provided an opportunity for him to contribute in his own way by serving the community and ensuring increased representation for nationalists and Catholics.
"The fact that Ronan Kerr took this decision in my opinion speaks volumes for his courage.
"I regard Ronan Kerr as a good Irishman I regard him as an Irish policeman and someone who took a very courageous decision, along with many others, to join the PSNI at a time of great change. And I hope young people will continue to do that."
Mr Robinson also urged young Catholics not to be deterred from joining the police "by those who have nothing to offer our society".
Mr Robinson, who spoke after a private meeting with the bereaved family, said: "He was the kind of communicator that came into the room and threw his arms around whoever was there, he came back and talked to anyone, the very kind of person that the PSNI needs, someone that can communicate on the ground."
The rookie officer had only graduated from training college last December.
He was one of the new crop of officers who had helped swell Catholic numbers to reach almost 30% of the service, as part of the new beginning to policing forged over the last decade.
It is widely believed that in an attempt to derail the cross-community support for policing, dissidents have specifically targeted Catholic recruits.
The explosion happened as the officer got into his car in the residential Highfield Close development, off the main Gortin Road, yesterday afternoon.
The blast shocked Omagh, where 29 people, including a woman pregnant with twins, were killed in the 1998 Real IRA car bomb attack.
It is understood the victim, a former pupil of the Christian Brothers Grammar School in Omagh, was leaving to start a shift at Enniskillen police station, Co Fermanagh, when he was killed.
People who knew him described the young officer as a kind person who always saw the good in others.
Mr Baggott appealed for anyone with information on the murdered officer's movements since Friday to come forward, especially if they had information on his car.
He said the vehicle was a black Ford Mondeo, registration PNZ 1114.
Northern Ireland Justice Minister David Ford added: "Ronan's murder was callous, it was calculating and it was cowardly."
He said: "It is absolutely clear that the small number of people intent on carrying out acts of terrorism stand totally against the wishes of the vast majority of the people of Ireland, north and south."
In Omagh, police were combing the area of the blast for clues about who was responsible.
Prime Minister David Cameron and Irish Taoiseach Enda Kenny condemned the bomb attack as a heinous and pointless act of terror.
US Secretary of State Hillary Clinton, whose husband, former president Bill Clinton, played a major role in the peace process, said her government strongly condemned the murder in Omagh.
Dissidents have carried out a string of similar attacks on PSNI officers in recent years and have shown a determination to identify Catholic officers in particular for attack.
Pc Stephen Carroll, 48, was gunned down in March 2009, just two days after the Real IRA shot dead two British soldiers at the Massereene Army base in Antrim.
And Pc Peadar Heffron was seriously injured when a device exploded under the driver's seat of his car in west Belfast in January 2010.
