Britain has one of the world's most stringent gun licensing systems - with owners of shotguns and rifles required to undergo background checks which are supposed to demonstrate that they pose no threat to public safety.
All applicants for licences to hold both shotguns and so-called Section 1 firearms must declare any criminal convictions, medical conditions or any previous treatment for depression or mental illness before their request is considered.
As well as providing details of their GP, those wishing to keep guns legally are obliged to give details of at least one referee and will usually be interviewed to establish that they have "good reason" to possess firearms.
Both types of licence are reviewed at five-yearly intervals and certificates, formally issued by Chief Constables, may be revoked if holders are deemed to be a danger to public safety, of "intemperate habits" or of unsound mind.
Weapons can also be confiscated or licences revoked if certificate-holders are judged unfit to keep firearms or to have no good reason to keep them.
Laws governing the estimated 580,000 shotgun certificate-holders in England and Wales also require weapons to be stored securely in an approved cabinet fitted to a brick wall.
Other elements of the UK's gun controls include a lifetime prohibition from keeping firearms or ammunition on anyone sentenced to more than three years in prison.
Commenting on the events in Peterlee, Shooting Sports Trust spokesman Mike Yardley warned against a "knee-jerk reaction" to the deaths.
Stressing that the vast majority of gun-related homicide and crime involved illegally-held firearms, Mr Yardley said: "Any applicant for a shotgun certificate will undergo a thorough background check.
"The applicant must provide GP details, a referee - two for a firearms certificate for section 1 firearms such as rifles - and show that he or she has somewhere safe to store a shotgun.
"He or she must also demonstrate to a Chief Constable that they represent no danger to public safety."
Mr Yardley added: "No licensing system can be perfect, but it would be hard to see how the present system could be much improved.
"We have very tough gun laws in the United Kingdom and we also have a very small amount of gun crime."