A member of police staff has been issued with a gross misconduct notice over their handling of Plymouth gunman Jake Davison’s application for a shotgun certificate and the later decision to return it to him weeks before the killings, the Independent Office for Police Conduct said.

Davison, 22, shot dead five people in Plymouth – including a three-year-old girl – during a 12-minute shooting spree.

The Independent Office for Police Conduct (IOPC) is investigating how the apprentice crane operator was originally granted a shotgun certificate in 2017 by Devon and Cornwall Police.

The watchdog is also examining how Davison was handed back the weapon and certificate weeks before the shooting having been seized after admitting two assaults.

Davison was placed on a voluntary intervention programme – an alternative to be charged or cautioned – after admitting assaulting two youths in park in September last year.

His shotgun and licence were not seized for another three months until concerns were raised directly with the police by a member of staff working on the intervention programme.

In July last year Davison was given back his shotgun and certificate, which he used for clay pigeon shooting.

On August 12, he shot his mother dead following a row at her home in Biddick Drive, Keyham

He then went outside and killed three-year-old Sophie Martyn and her father Lee, 43, in front of horrified onlookers as they walked their pet dog in Biddick Drive.

Davison then shot Stephen Washington, 59, in a nearby park, before shooting Kate Shepherd, 66, on Henderson Place. He then turned the gun on himself before armed officers reached him.

The IOPC said the police staff member who handled Davison’s original shotgun application and also decided to return the weapon would be issued with a gross misconduct notice.

A police officer who investigated the assault against Davison would be issued with a misconduct notice.

The IOPC said it was investigating whether they shared information appropriately with the force firearms and explosives licensing department regarding Davison’s admitted involvement in a violent offence, and whether they took appropriate steps to seize the shotgun certificate, shotgun, and ammunition.

IOPC regional director David Ford said: “Based on the evidence gathered so far, we have now served disciplinary notices on two individuals within the force to advise them their conduct is subject to investigation.

“The serving of such notices will be kept under review.

“We intend to complete our investigation before the end of this year. We will share any lessons that may be learned with the force and wider organisations as they emerge.

“At the conclusion of our investigation, we will decide whether any individual has a disciplinary case to answer.”

An inquest has previously been opened and adjourned with Davison’s victims all dying from shotgun wounds. Davison had also suffered fatal shotgun wounds having turned the weapon upon himself.

As well as the coroner’s investigation and IOPC inquiry, the National Police Chiefs Council is also looking at the Devon and Cornwall force’s firearms policies and procedures.

The Government is planning new statutory guidance, including asking doctors to undertake medical checks on anyone applying for a licence and inquiries into social media usage.

Davison received mental health support during the coronavirus lockdown and had been in contact with a telephone helpline service in Plymouth run by the Livewell Southwest organisation.

Social media usage by Davison suggested an obsession with “incel” culture, meaning “involuntary celibate”, as well as an interest in guns and the US.

Reports have suggested Davison’s mother had been struggling to get help for her son, having become concerned about his mental health.