Britain's interior ministry on Monday asked police to review the social media accounts of people applying for gun licences and revisit existing permits, after the country's worst mass shooting since 2010.
On Thursday Jake Davison, 22, shot and killed five people -- including his mother and a three-year-old girl -- in Plymouth in southwest England before taking his own life.
His social media accounts revealed misogynistic views and an interest in right-wing politics, guns and violent video games.
But the local police restored Davison's gun licence and his weapon in July months after they had been removed following an assault allegation -- a decision now being scrutinised by the police watchdog.
The UK government is planning to publish guidance on firearms licensing applications that will affect all 43 police forces in England and Wales.
"Incidents such as Thursday's horrific events in Plymouth are thankfully rare, but their impact is profound," an interior ministry source said.
"Today, as a matter of urgency, we are asking the police to review their practices and whether any existing licences need to be looked at again.
"This will help reassure people that all necessary checks have been made to keep them safe."
Britain has low gun crime rates and strict controls on the ownership of firearms, with most police unarmed.
Only four percent of homicides were caused by shooting in England and Wales in the year to March 2020, according to the latest government figures.
Licences are granted for sporting rifles and shotguns only after stringent background checks, including character references and mental health assessments.
Private ownership of firearms is banned in nearly all cases.
Plymouth observed a minute's silence in memory of the victims at 11:00 am (1000 GMT).
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