Senior police officers were "distracted completely" by planning for the G7 summit in Cornwall in the weeks before the fatal Plymouth shootings, an inquest has heard.
Two months after the gathering of world leaders in 2021, the biggest and most complex event undertaken by Devon and Cornwall Police, Jake Davison shot dead his mother and four others with a pump-action shotgun in the Devon city of Plymouth.
At an inquest into the death of his victims on Friday, Superintendent Kara Sherwood said: "Senior officers went off to plan the G7 and were distracted completely."
She also said that the force's firearms department was "fundamentally under-staffed" in the run-up to the shooting.
She disagreed with Dominic Adamson KC, representing the victims' families, who asked if the safety of world leaders was more important than firearms in the region.
Davison, a 22-year-old apprentice crane operator, killed his mother, Maxine Davison, after an argument then went out on to the street.
He shot dead Sophie Martyn, three, her father Lee Martyn, 43, Stephen Washington, 59, and Kate Shepherd, 66, in the Keyham area of the city before turning the gun on himself.
The force had taken away his shotgun and licence in 2020 after he assaulted two teenagers in a park, but returned them to him weeks before the killings in August 2021.
Ms Sherwood was also asked what she would do in the scenario of a violent offender whose weapon had been seized.
She said: "I would not return the weapon if it was a particularly violent assault. It is a high-risk decision."
The inquest heard Davison declared that he had autism on his application, and gave consent for his GP to share information with police about his medical history.
However, Davison's GP refused to provide an opinion to police assessing whether he should be issued with a shotgun certificate.
Chief Superintendent Roy Linden, of Devon and Cornwall Police, told the inquest police should have collected medical evidence about Davison when considering his application for a shotgun licence.
He told the inquest: "Opinion should have been sought from a GP."
Addressing the families of the victims, Ms Sherwood also said it was "unimaginable" what they were going through and that the incident had "affected us all personally and professionally".
She added: "We, and others, will learn from this."
The inquest continues.