(a) "The gun was made on a 3D printer that cost $8,000 (£5,140) from the online auction site eBay.
"It was assembled from separate printed components made from ABS plastic - only the firing pin was made from metal.
(b) "To make the gun, Mr [Cody] Wilson[, a 25-year-old law student at the University of Texas,] received a manufacturing and seller's licence from the US Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) [a license need to sell that gun].
"Donna Sellers, from the ATF, told BBC News that the 3D-printed gun, as long as it was not a National Firearms Act weapon (an automatic gun, for example), was legal in the US.
"She said: '[In the US] a person can manufacture a firearm for their own use. However, if they engage in the business of manufacture to sell a gun, they need a licence."