Beyond belief hardly does it justice.http://www.bbc.co.uk/news/world-us-canada-22386105
Kristian's rifle was manufactured by Keystone Sporting Arms, which has a "kid's corner" on its website featuring images of children at shooting ranges and on bird and deer hunts.
The guns are sold in pink, blue and other colours and designs.
In the last three days at least three young boys have shot their sisters in the US, says Daily Kos writer David Waldman, who tracks accidental shootings.
In addition the Sparks case, a five-year-old girl was shot and killed by her eight-year-old brother in western Alaska on Tuesday, while a seven-year-old boy shot his sister, nine, in the leg in Auburn, Washington on Thursday.
Kentucky state lawmaker Robert Damron, a Democrat, said: "Why single out firearms? Why not talk about all the other things that endanger children, too?"