In fact, there are a number of sources that allow guns to fall into the wrong hands, with gun thefts at the bottom of the list. Wachtel says one of the most common ways criminals get guns is through straw purchase sales. A straw purchase occurs when someone who may not legally acquire a firearm, or who wants to do so anonymously, has a companion buy it on their behalf. According to a 1994 ATF study on "Sources of Crime Guns in Southern California," many straw purchases are conducted in an openly "suggestive" manner where two people walk into a gun store, one selects a firearm, and then the other uses identification for the purchase and pays for the gun. Or, several underage people walk into a store and an adult with them makes the purchases. Both of these are illegal activities.
The next biggest source of illegal gun transactions where criminals get guns are sales made by legally licensed but corrupt at-home and commercial gun dealers. Several recent reports back up Wachtel's own studies about this, and make the case that illegal activity by those licensed to sell guns, known as Federal Firearms Licensees (FFLs), is a huge source of crime guns and greatly surpasses the sale of guns stolen from John Q. Citizen. Like bank robbers, who are interested in banks, gun traffickers are interested in FFLs because that's where the guns are. This is why FFLs are a large source of illegal guns for traffickers, who ultimately wind up selling the guns on the street.