The .22 caliber rifle used in Tuesday's tragedy is marketed by Crickett to young ones with the slogan "My First Rifle." It had been left loaded with a single shell in a corner of the family's home.
But unlike other similar cases, the weapon actually belonged to the child from Cumberland County in Kentucky. He had received it last year as a gift.
"Just one of those crazy accidents," Cumberland County Coroner Gary White told The Lexington Herald-Leader. "It's a little rifle for a kid... The little boy's used to shooting the little gun."
Crickett declined to comment on the matter. The rifle can be purchased in green, blue or pink, for girls.
The shooting triggered outrage in the United States, still reeling from the shooting of 20 small children and six adults and Sandy Hook Elementary School in Newtown, Connecticut.
Anti-gun lobby group Americans for the Protection of Children has launched an online petition to "stop Crickett Firearms, the NRA (National Rifle Association) and its allies from marketing guns to our kids."
The NRA is planning to host a youth day on Sunday during its annual convention in Houston, Texas, featuring gun manufacturers who design weapons especially for children.
"It's appalling," the petition said about the youth day.
Crickett's website, which was no longer accessible Thursday, had published dozens of photographs of children handling rifles -- including a baby dressed in a camouflaged-patterned romper, grasping a weapon resting on its knees.
The Pennsylvania-based manufacturer of Crickett rifles, Keystone Sporting Arms, says it has sold 4,000 rifles when it first started in 1996, compared to 60,000 in 2008.
It says it aims "to instill gun safety in the minds of youth shooters and encourage them to gain the knowledge and respect that hunting and shooting activities require and deserve."
Weighing just 2.5 pounds (1.1 kilograms) with a barrel measuring 16 inches (40 centimeters) for a total length of 30 inches (76 centimeters), the rifle can only shoot one shell at a time and its trigger can be locked. It costs $110 to $140 depending on the model and can easily be purchased at big retailer Walmart.
On firearms discussion forum "The Firing Line," parents have been known to write enthusiastically about rifles purchased for children as young as three.
"I'm just excited he wants to hear it go bang and be there with me. I could care less what he hits, everything is a bullseye at this point," user Saltydog235 wrote about his four-year-old in 2010.
"He's learning gun safety and handling which is more important than accuracy at this juncture as well."
Violence Policy Center executive director Josh Sugarmann said there is a "wide range" of guns targeted toward the youngest Americans.
"The gun industry and gun ownership is declining, it has been for decades, and like tobacco, the industry needs new customers," he told ABC News.
"The most vulnerable years to entice children as future gun customers is during their youth."
And in a bid to attract more customers, groups largely funded by the gun industry organize youth competitions and internships.
Gun violence kills more than 3,000 children and teens, and injures more than 15,000 each year in the United States, according to the American Academy of Child and Adolescent Psychiatry. That's more deaths than the number of US soldiers killed in nearly nine years of war in Iraq.
In this country, where the right to bear arms is enshrined in the constitution and with about as many weapons in the country as the 310 million Americans, accidents involving guns with the very young are far from rare.
A six-year-old shot and seriously wounded his four-year-old friend in New Jersey with a shot to the head in early April. Just two days earlier, a four-year-old killed a woman during a family barbecue in Tennessee.
"It IS something you can prepare for, by storing the gun locked and unloaded, or by avoiding having guns in homes with children," said Kid Shootings, a blog by authors from Ceasefire Oregon Education Foundation, Protect Minnesota and States United Against Gun Violence.
"You don't have to accept that it was 'her time to go' when it was completely avoidable."