WASHINGTON (AP) — FBI Director James Comey says the gunman charged in the Charleston church massacre should not have been allowed to purchase the gun used in the attack.

Comey on Friday attributed the problem to incomplete and inaccurate paperwork related to an arrest of Dylann Roof weeks before the shooting.

He says an FBI examiner who looked into Roof’s background when he tried to purchase a gun never saw an arrest report in which police say he admitted to possessing drugs. The arresting agency was listed erroneously on the rap sheet that the examiner reviewed.

Under FBI rules, that admission should have disqualified Roof from being able to buy a gun.

The transaction went through after three days because the examiner didn’t have enough information to authorize or deny it.