IANSA director Rebecca Peters said: "The idea that only 'bad guys' do things like this is false.
"People who are not career criminals can turn violent. Having weapons designed to kill people is dangerous.
"The gun lobby says legal gun holders are not a problem at all and what we have to worry about is career criminals.
"But these are not career criminals, they're normal people, so that's an argument for recognising that just checking someone's criminal background is not enough to prevent homicides."
The killings showed the importance of strict controls on who should be allowed to own guns and what type, she added.
"In Britain the controls are strict compared with many other countries," she said.
"But this is yet another example of how a law-abiding gun owner can turn very suddenly into not law-abiding and the fact that they have been previously law-abiding does not mean they're responsible enough to own guns."
The answer is clear: fewer guns, and the ones that are allowed have to be licensed and registered in the strictest way possible. Truly law-abiding gun owners would applaud such initiatives.
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