As a dealer, I was the last line of defense to prevent guns from falling into the wrong hands. I had a computer terminal that the person buying the gun would fill out Part A of the form 4473 and answer several questions. When that was complete, I filled out Part B and then called a phone number that went directly to the FBI. I read the applicant's Name, social, DOB, type of gun being purchased (long gun) and waited while a background check was done. The answer would come back Proceed, Denied, or Delay
Part A question 11 (a),(d), or (h) either one alone if answered truthfully would have stopped this sale in its tracks. Both (d) and (h) had to have been answered falsely.
all this said, perhaps they bought the firearm from an individual and no background check at all was done. it happens all the time.
https://www.atf.gov/file/61446/download