According to an FBI database, the Department of Defense, as a whole has only reported one domestic violence conviction.

But the Department of defense says that number isn't correct.

The question remains -- how did Devin Kelley slip through the cracks -- despite having a domestic violence conviction?

Right now, we really don't know.

But what we do know is that the Air Force failed to report Kelley's domestic violence conviction to the National Criminal Information Center database.

That database is just one used to run background checks on anyone trying to buy a gun. The Colorado Bureau of Investigation typically uses seven databases to run background checks.

Because his information wasn't entered, Kelley wasn't flagged.

The Air Force has since launched a review of how the Service handled Kelley's criminal records.

But, are there others like Kelley?

According to these FBI records, as of last year the Department of Defense as a whole only reported just one domestic violence conviction and it came from the Navy.

We called the DOD for comment, a spokesman told us that number is wrong. But he didn't tell us an accurate number of domestic violence claims. He said the DOD doesn't report to that specific FBI database.

Jessica Higgins with The Initiative, a domestic violence advocacy organization, says we need to do better.

"For individuals who have committed violence against their spouses or partners in the past, they absolutely should not be able to get access to a gun because the likelihood that they will use that gun to kill their partner is so high," she said. "We're now finding with these new studies is that the likelihood that they will go out and harm large numbers of people outside of just the relationship itself is so high."

Today, we confirmed that the Department of Defense is doing a deeper review of its reporting, in addition to the work the Air Force is doing to review Kelley's case.

9NEWS has put several calls into the FBI and is still waiting to hear back.