British police said on Friday they were investigating the background of a troubled loner who obtained a firearms licence and shot dead five people including a three-year-old girl in the country's first mass shooting in 11 years.

No motive has yet emerged for Thursday evening's bloodshed at the hands of 22-year-old gunman Jake Davison, who killed himself after the six-minute spree in a quiet residential area of Plymouth, southwest England, not far from western Europe's biggest naval base.

But Devon and Cornwall Police ruled out terrorism, including with far-right groups, and said there was a “familial relationship” with Davison's first victim aged 51, while declining to confirm local reports that she was his mother.

After killing the woman at her house, Davison shot and killed the toddler and her male relative aged 43 on the road outside, before taking the lives of a man and woman nearby, the police said.

Another two local residents received “significant” but not life-threatening gunshot wounds, Chief Constable Shaun Sawyer told reporters, adding that as of 2020, Davison held a valid firearms licence.

Local and national leaders expressed shock and grief. But as questions mounted over Davison's past and the police response, Prime Minister Boris Johnson thanked the emergency services.

“My thoughts are with the friends and family of those who lost their lives and with all those affected by the tragic incident in Plymouth last night,” he tweeted.

Tough gun laws

A single gun was recovered from the scene after Davison shot himself, but the police chief was unable to confirm witness accounts that it was a pump-action shotgun.

Britain has some of the Western world's toughest gun controls and police are not routinely armed.

Private ownership of handguns was outlawed in nearly all cases after a school massacre in the Scottish town of Dunblane in 1996, which claimed the lives of 16 young pupils and their teacher in Britain's worst mass shooting to date. But ownership of sporting rifles and shotguns is allowed, subject to strict licensing rules.

Licences last five years, and are meant to be granted only after thorough police background checks, including for mental illness.

Britain's last mass shooting was in June 2010, when taxi driver Derrick Bird killed 12 people in Cumbria, northwest England.

YouTube rants

Davison's social media channels indicated an interest in guns, right-wing libertarian politics and “shoot-em-up” video games.

The content suggested a self-pitying loner, alienated from his family and hostile to women.

On Facebook, Davison said he was originally from the US city of Phoenix, Arizona, but that was not substantiated in local accounts.

He listed his employer in Plymouth as Babcock International, a UK engineering services company active in the city's naval docks.

He was reportedly a trainee crane operator in the docks, after working as a scaffolder in his late teens.

YouTube deleted his own content on Friday morning. Prior to being taken down, it mostly showed him lifting weights in his home gym.

In one message to the camera, in a strong English west-country accent, he ranted about women in misogynistic terms. In the last upload, on July 28, he spoke of feeling “beaten down and defeated” by life.

The last external video he “liked” on YouTube, this week, was of a series of shots fired from a World War II US rifle.

Sawyer defended the police response, insisting that armed response units were quickly at the scene, but too late to engage with Davison before he killed himself.

“We believe we have an incident that is domestically related that has spilled over into the streets,” said Sawyer, adding that police were examining Davison's social media activity, hard drives, and home life.

The chief constable said he could not confirm whether Davison's firearms licence covered the weapon used on Thursday.

An “independent review” would look into how he obtained the licence, and whether the gunman had any mental health issues.