An inquiry has found that Durham Police made ?inexcusable? blunders when dealing with a man who later shot dead three people with legally-held firearms.

Michael Atherton, aged 44, shot his partner and two other family members before shooting himself dead after an argument at his home in Horden, on New Year’s Day.

He legally owned six weapons, including three shotguns, but an investigation by the Independent Police Complaints Commission (IPCC) has concluded that his violent past had not been properly investigated by Durham Police.

A copy of the IPCC’s report into the incident, seen by the BBC, concluded that police knew of a number of incidents which should have cast doubt on Atherton’s suitability to hold firearms.

Though Atherton had never been arrested, the police were aware of a history of domestic violence and drunken assaults before he applied for a shotgun certificate in 2006 and a firearms licence two years later.

Shortly after being granted the firearms licence, Atherton’s weapons were seized after another incident at his home, but were later returned without Atherton or his family being formally interviewed by licensing staff.

Durham’s deputy chief constable, Michael Banks, said: ?We’ve been informed by the IPCC that it is its recommendation that there are no criminal or misconduct cases to answer. Since the tragic events in January, we have carried out a full review of policy and procedures. It would be wholly inappropriate to comment further.?

BASC criticised the IPCC for leaking the results of its inquiry months before it was expected to be made public, but said it was not shocked by the inquiry’s conclusions.

Director of firearms, Bill Harriman, said: ?We were unsurprised to learn that there were serious failings by Durham Police, but we are concerned to learn that no disciplinary action is to be taken against any member of the force.?

?Durham Police’s concern that it might have lost an appeal, had it revoked Atherton’s certificates, lacks credibility and substance – in our experience, the chances of him winning any appeal were slight.?