A member of police staff has been handed a gross misconduct notice following the Plymouth gunman Jake Davison’s shooting spree that saw five people killed in August.

Davison killed his mother Maxine Davison, 51, during his gun rampage as well as three-year-old Sophie Martyn and her father Lee Martyn, 43; Stephen Washington, 59 and Kate Shepherd, 66 before turning the gun on himself.

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

The incident was the first mass shooting in Britain since June 2010, when taxi driver Derrick Bird killed 12 people and injured 11 others in Cumbria.

Davison, 23, grew up in the United States and appeared in YouTube videos where he spoke about how he was “defeated by life” weeks before the mass shooting.

Independent Office for Police Conduct issue statement following investigation into Plymouth shooting

IOPC regional director David Ford said: “I again offer my heartfelt sympathies to all those affected within the Plymouth community and beyond by the traumatic events of August 12.

“We still have significant investigative work to undertake but continue to make good progress with our inquiries.

“We are reviewing a substantial amount of information gathered from Devon & Cornwall Police and elsewhere and the force has continued to co-operate fully with our independent investigation.”

He continued: “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. We expect to submit a final investigation report, which will set out our findings, to the coroner and Devon & Cornwall Police in December.

“We appreciate the significant public interest in the inquiries taking place. In view of the inquest proceedings, the timing of publication of our findings will be determined following consultation with the coroner.”