The way Northern Ireland addresses its violent past is not working, the Police Ombudsman said.
The grandchildren of those involved first-hand are seeking answers and Dr Michael Maguire said he could only provide partial explanations.
The independent watchdog, who investigates alleged wrongdoing by officers, said he had less staff now than five years ago - with more than double the number of legacy cases on his books.
“Sometimes I am very optimistic, I think the smoke signals are there that something is going to happen.
“On other occasions I get totally depressed because I think that this isn’t what is happening and we are going to be left with a fragmented, ad-hoc, underfunded way of dealing with very complex issues.
“Should it happen? Absolutely, because what we have at the minute isn’t working.”
Mechanisms were agreed in 2014 as part of the Stormont House Agreement to address the legacy of thousands of unresolved murders but they have not been established yet.
One of the main stumbling blocks was national security and how sensitive information was handled and released publicly.
Sinn Fein wants an independent voice to make the final decision on what level of detail should be made available to families of victims of the Troubles.
Northern Ireland Secretary James Brokenshire is expected to launch a public consultation soon on addressing the past.
Proposed institutions agreed at Stormont House included a historical investigations unit which will attempt to prosecute perpetrators, an information retrieval body allowing victims to receive information privately, an oral history archive and a system for dealing with historical inquests.
Mr Maguire said past efforts to tackle the issue had suffered problems.
“So we need a better way of doing it, we need a better way of answering the questions and addressing in a realistic term what dealing with the past means.
“Because quite often expectations about criminal justice solutions are unrealistic but there are other things that can be done.”
He said the Stormont House institutions would be a better way of tackling the criminal justice dimension.
“I can only deal with the police, I cannot deal with the military, I cannot deal with any other agencies, I cannot deal with the paramilitary who pulled the trigger.
“A comprehensive approach to dealing with the past through an historical inquiries unit can do that and will have the powers of compellability across the state that I don’t have and will have the ability to look at those who actively were involved in terrorist attacks.”
Dr Maguire participated in Alex Gibney’s No Stone Unturned documentary about the Loughinisland shootings at a country pub in Co Down.
The watchdog’s report said last year there was collusion between some police officers and loyalist gunmen who killed six Catholics while they watched a Republic of Ireland football match in 1994.
He said there was no evidence police had prior knowledge of the Ulster Volunteer Force (UVF) attack. The identities of the alleged killers were not disclosed in Dr Maguire’s report.
He was quizzed after a special screening of the documentary in Belfast.