able to buy the 45 caliber gun used in the slaughter. that admission coming from fbi director james comy who told reporters his bureau made a mistake during dylann roof's background check and he says that rips all of our hearts out. according to law enforcement days after the shooting agents on the ground new something was amiss and suspected that roof's arrest record should have prohibited the gun purchase. >> it just shows how a bureaucratic mistake can cost human life. >> reporter: they didn't discover roof had previously admitted to illegally possessing drugs when he was arrested in late february. that information would have prevented roof from passing the background check. >> there's a regulation that says if he was a drug user, he shouldn't have got a gun and there was a abundant information for the fbi to have had that information. had they had it, no gun sale and possibly no shooting here.