He added that his son, the victim's husband, is now grappling with how to break the news to the youngster, the couple's only child.
"He has a 2-year-old boy right now who doesn't know where his [mother] is and he'll have to explain why [she] isn't coming home," he said.
"And then, later on his life, as he questions it more, he'll again have to explain what happened, so we'll have to relive this several times over."
Around 30,000 deaths a year in the United States involve firearms. The majority are suicides; many others are murders. But some involve children laying their hands on loaded weapons. In 2011 alone, 140 children and teenagers died as a result of an unintentional shooting, according to a study from the Brady Centre to Prevent Gun Violence.
"Every day as parents, we make rational choices regarding our family's safety - we buckle our children's seatbelts, make them wear bicycle helmets, and teach them to look both ways before crossing the street.
"But when it comes to gun safety, many parents do not take the same logical approach," the centre said.
The Wal-Mart retail chain is the biggest gun retailer in the US, which has seen a rise in gun buying in recent years among women looking for greater personal protection.
Concealed weapons are part of everyday life in the Mountain West state of Idaho.
Like other Western states, gun rights are a big issue there. State politicians passed legislation last year allowing concealed weapons on the state's public college and university campuses. Despite facing opposition from all eight of the state's university college presidents, the legislators sided with advocates who said the law would better uphold gun rights.
About 7 per cent of adults in Idaho had concealed weapons permits at the end of 2012, according to the Crime Prevention Research Centre in Swarthmore, Pennsylvania. Kootenai County, which has about 140,000 residents, has issued close to 16,000 concealed weapons permits to residents, Kootenai County sheriff's spokesman Stu Miller said.
-AFP, AP