Kelly said he plans to surrender the AR-15 to Tucson police, KTVK-TV, Phoenix, reported.
"It's important for me to have first-hand knowledge about how easy it is or difficult it is to buy a weapon like that," Kelly said. "For a weapon that's so deadly, and really designed for the military especially with the high capacity magazines, it's a pretty easy thing to do, even with a background check."
Giffords suffered a traumatic head injury Jan. 8, 2011, when Jared Loughner, a community college student, opened fire at a meet-and-greet outside a Tucson supermarket. She and her husband, a Navy officer and NASA shuttle commander, have founded Americans for Responsible Solutions, a group that pushes for expanded background checks for gun buyers.
Kelly said he bought a handgun he intends to keep from the store and then decided to purchase an AR-15.
Douglas MacKinlay, the store owner, told KTAR, Phoenix, he checked that Kelly was an Arizona resident when he produced only a Texas license, making him return with additional proof of residency. MacKinlay said he recognized Kelly.
"We were certainly wondering what his intent was," MacKinlay said. "But it is not for us to question a customer, other than to question that they are a lawful purchaser and that they don't have any criminal intent to use that firearm."