The killing of journalist Lyra McKee has led to a "palpable change" in community sentiment in support of policing in Northern Ireland, a senior detective has said.
Ms McKee, 29, was shot while observing rioting in Londonderry's nationalist Creggan estate on Thursday.
Two men, aged 18 and 19, arrested under the Terrorism Act were released without charge on Sunday.
Det Supt Jason Murphy urged people to come forward with evidence.
Speaking on Saturday, the detective leading the investigation said there was a sense that what had happened to Ms McKee had marked a "real sea change".
He also warned that he had a broader concern about a "new breed of terrorist coming through the ranks".
"And that is very worrying for me," he added.
But he said that police officers had felt a "palpable" change in the community sentiment towards policing.
"Yesterday we realised that the vast majority of communities across the whole of Northern Ireland support policing and support police and they support the peace process," added Mr Murray.
"What we saw yesterday was the visible demonstration of that within the Creggan community.
"A community that has been very frightened for a long time and for a large part has been held to ransom by terrorist organisations that claims to represent them."
Ms McKee was standing near a police 4x4 vehicle with other journalists when she was shot on Thursday night.
CCTV captured her final moments in the crowd and mobile phone footage showed the suspected gunman.
In the video, the masked attacker can be seen leaning from behind cover and appears to fire shots towards police and onlookers.
The Police Service of Northern Ireland (PSNI) said that the gunman fired shots towards police officers at about 23:00 BST on Thursday.
In a Facebook post, the political party Saoradh - a group that police have said is closely aligned to the New IRA - sought to justify violence on the night.
They said Ms McKee was killed "accidentally" by a "volunteer" after the PSNI raided houses in Derry in search for weapons and ammunition.
Who are the New IRA?
The New IRA was formed in 2012 after a number of dissident republican organisations said they were unifying under one leadership and is believed to be the largest dissident republican organisation.
Saoradh, which means liberation in Irish, is a political group that was founded in 2016 and has the support of prisoners from the dissident group referred to as the New IRA.
According to its constitution, Saoradh's objective is to "effect an end to Britain's illegal occupation of the six counties" and establish a 32-county Irish socialist republic.
The party has been highly critical of Sinn Féin in the past, with its chairman describing members as "false prophets who have been defeated and consumed by the very system they claim to oppose".
There has been widespread condemnation of the killing.
At a vigil in Derry on Friday, Ms McKee's partner Sara Canning described her as a "tireless advocate and activist" for the LGBT community.
Her partner's dreams had been "snuffed out by a single barbaric act", said Ms Canning, and she had been left without "the woman I was planning to grow old with".
Ms McKee's killing came 21 years after the Good Friday peace agreement was signed in Northern Ireland.
The 1998 peace deal marked the end in the region of decades of violent conflict - known as the Troubles - involving republicans and loyalists during which about 3,600 people are estimated to have died.
The Good Friday Agreement was the result of intense negotiations involving the UK and Irish governments and Northern Ireland's political parties.
Figures from across the political divide, including Sinn Féin leader Mary Lou McDonald and Democratic Unionist Party (DUP) leader Arlene Foster, were among the hundreds of people at a vigil in the Creggan estate on Friday.
Northern Ireland Secretary Karen Bradley visited Derry on Saturday to sign a book of condolence.
Sec of State today made a private visit to Derry-Londonderry to sign the book of condolence for Lyra McKee and thank PSNI for their hard work. She wrote: "A tragic loss, such promise, such energy, so much potential. We can only imagine what you would have achieved." pic.twitter.com/jC40W0uMoB— Northern Ireland Office (@NIOgov) April 20, 2019
Other political figures united to condemn Ms McKee's killing.
Former US President Bill Clinton said he was "heartbroken".
Heartbroken by the murder of Lyra McKee and the violence in Derry. The challenges in NI today are real--but we cannot let go of the last 21 years of hard-won peace and progress. This tragedy is a reminder of how much everyone has to lose if we do.— Bill Clinton (@BillClinton) April 19, 2019
Irish President Michael D Higgins signed a condolence book at Belfast City Hall and said there was "outrage" in Ireland.
The EU's chief Brexit negotiator Michel Barnier tweeted that Ms McKee's killing was a "reminder of how fragile peace still is in Northern Ireland".