Gun sales have been rising as fears grow of tougher regulations in the wake of San Bernardino and other mass shootings, and there are now moves by gun control campaigners to overturn a controversial law that protects gun dealers and manufacturers
Colby Sue Weathers had suffered from severe mental illness most of her adult life. In her thirties, she was diagnosed with paranoid schizophrenia and in May 2012 she tried to kill herself with a gun she bought from a pawn shop.
Her family, from Wellington, Missouri, managed to take that gun away, but a month later they feared she was planning to buy another from the same store.
Her mother, Janet Delana, called Odessa Gun and Pawn to warn them: "I told them who I was, I told them my daughter's name and social security number.
"I told them she's ill and paranoid schizophrenic, she's currently cycling out of control and she does not need to have a gun," she said.
"I said please don't do that, don't sell it if she comes in - but I don't think they took me seriously at all."
According to court records, on 27 June 2012, two days after her mother's phone call, Colby was sold a .45 calibre semiautomatic pistol. She returned to her home and an hour later, shot and killed her father Tex.
Colby was acquitted of murder due to her mental illness and is receiving hospital treatment. But charges of negligence against Odessa Gun and Pawn were dismissed by a trial court earlier this year.
Janet Delana is appealing against the decision in the Missouri Supreme Court in December.
"The main issue in this case is that the gun dealer should have used reasonable care," says Jon Lowy, director of the legal action project at the Brady Center to Prevent Gun Violence, an advocacy group that is supporting Mrs Delana.
"If they're told that somebody is mentally ill and dangerous and shouldn't have a gun, they should not sell them a gun or at least look into it."
The case is being pursued on grounds of negligence because other legal options are limited by the 2005 Protection of Lawful Commerce in Arms Act.
"The act gave the gun industry protection from civil justice laws that no other industry in America has," says Lowy. "There have been cases where gun dealers have done things that were negligent, and yet they've been given protection."
Only two claims for damages against gun dealers have reached court since the act came into force and only one has been successful.
In October 2015, Badger Guns was ordered by a Wisconsin court to pay almost $6m to two police officers who were shot with a weapon bought illegally from the retailer.
Democratic presidential frontrunner Hilary Clinton has pledged to overturn the law, often referred to as the Immunity Act. And she's not alone - many state legislators are also making gun safety a central part of their election campaigns.
In the wake of the October shooting at an Oregon community college that left nine people dead, President Barack Obama urged Americans to vote only for lawmakers who support gun control.
For the first time since 2012 when 20 children were killed in a mass shooting a school in Newtown, Connecticut, the issue is back on the political agenda.
"We've not seen that in previous elections," says Lowy. "These are smart politicians. They believe in doing the right thing but they also believe in getting elected.
"They know 90% of people support gun safety and there's a good political reason to embrace this issue."
Candidates who support gun control are also getting millions of dollars from Everytown for Gun Safety, an advocacy group set up last year by billionaire and former New York Mayor Michael Bloomberg.
It's the first real challenge to the National Rifle Association which also spends millions of dollars supporting the Second Amendment - the constitutional right of Americans to bear arms.
'No blanket immunity'
But many gun dealers are sceptical that overturning the Immunity Act or imposing extra controls will stop guns falling into the wrong hands.
"The Protection of Lawful Commerce in Arms Act protects gun dealers and gun manufacturers from frivolous lawsuits that were a backdoor way to try to put us out of business," says David Zeller, a federally licensed dealer and owner of Zeller's Sporting Goods, Pennsylvania.
"It does not give us blanket immunity."
He says dealers can still be prosecuted if they fail to do a background check or knowingly sell a gun to a straw purchaser - a person who buys a gun on behalf of somebody who isn't legally permitted to have one.
"The real issue is having a bad person committing a bad act.
"If someone drives a vehicle drunk and runs over three people, we don't go after Ford Motor Company if they were driving a Ford - we try to hold that person individually responsible.
"We should do the same thing with guns," says Mr Zeller.
Dealers also say that tighter regulations won't help them identify people who are mentally ill. For the most part, a person's medical history is not revealed in background checks.
"I have to ask people for their social security number and they already freak out over that," says Benjamin Brown, an Air Force veteran, federally licensed dealer and owner of Landmark Firearms, Pennsylvania.
"They're not going to tell me their whole medical record."
The Brady Center says the vast majority of licensed dealers operate within the law, but unregulated private sales allow almost anybody to buy a gun without a background check.
Tighter restrictions are simply a sensible measure, say advocates.
Few dealers dispute that guns fall into the wrong hands but are divided over what to do about it. More regulation that puts an extra burden on law abiding citizens, they argue, is not the answer.
More than 380 people have been killed in mass shootings in the US this year. And in the wake of high profile killings in South Carolina, Virginia and Oregon, more and more states are introducing local gun control legislation.
But the issue remains one of the most divisive in the US today and it remains to be seen whether Congress will follow suit.