According to a recent report by Spain's Vanguardia, a company has installed vending machines selling bullets in grocery stores in several states in the United States, including Alabama, Oklahoma and Texas. Customers can buy bullets at the same time as they buy milk.

American Bullet reportedly said its vending machines use ID scanners and facial recognition software to verify customers' ages and are as "quick and easy" to use as a tablet.

However, this has also sparked concerns that selling bullets in vending machines will lead to more shootings in the U.S. On July 4, Independence Day, gun violence killed at least 33 people this year alone.

The company argues that age-verification technology means the transaction is as safe or even safer than online sales, which may not require proof of age, or risk theft in retail stores.

"Age verification and continuous sales tracking are promising safety measures that belong in gun stores, not where you buy your kid's milk," said Nick Suplina, senior vice president of legal and policy at EveryCity for Gun Safety. "In a country where guns and ammunition are rampant and the leading cause of death among children, we should not further normalize the sale and promotion of these products." Federal law requires that you must be 18 to purchase shotgun and rifle ammunition and 21 to purchase handgun ammunition.