CINCINNATI – Even though it looked like a rifle, the gun used to kill nine people and wound at least 14 more was likely classified as a pistol, skirting laws restricting short-barreled rifles.

Will the device on Connor Betts' weapon, called a "pistol brace," become the next bump stock in nation's gun control debate?

Here's what we know about the AR-15 style .223 caliber firearm used in the Dayton shooting Sunday:

It was legally purchased by Betts' from an online retailer in Texas. It then was transferred to him by a local firearms dealer who would be required to perform a background check, police said.

Nothing on Betts' criminal record would have prevented him from buying a gun.

He used legal-to-own 100-round drum magazines.

The lower receiver, which houses the trigger, was made by Anderson Manufacturing in Hebron, Kentucky. Under federal law, the lower receiver is the gun. Purchasing a lower receiver requires a background check. All other parts of guns, such as barrels and stocks, can be bought legally off the shelf or online.

Betts could have had as many as 250 rounds in his possession; he fired at least 41 rounds in about 30 seconds.

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On Monday, Dayton Police Chief Richard Biehl said Betts' gun was "modified in essence to function like a rifle" and "to avoid any legal prohibitions." He did not specifically cite a pistol brace, but photos of the weapon released by police show one.

The federal restrictions on short-barreled rifles were enacted to stop people from making rifles, guns fired from the shoulder, more concealable. Rifles typically can fire more powerful cartridges than pistols and shoulder stocks allow the rifles to be fired more accurately.

It is illegal to own a rifle with a barrel shorter than 16 inches without paying $200 for a National Firearms Act tax stamp and completing all the related paperwork and background checks. The process is similar to legally owning a fully automatic rifle.

It is unclear if Betts' went through this process, but the firearm he used did have a barrel shorter than 16 inches.

AR-15-style firearms can be rifles or pistols. A pistol can have a short barrel, but no shoulder stock. A rifle can have a shoulder stock, but the barrel must be 16 inches or longer.

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Enter the pistol brace, also known as a stabilizing brace. For all practical purposes, this device allows pistols with short barrels to have something resembling a shoulder stock.

Companies began marketing pistol braces in the early 2010s after getting approval letters from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives. The braces are designed to be strapped to the arm, allowing AR-15-style pistols to be more easily fired with one hand.

Many of these devices closely resemble shoulder stocks and can be used in that fashion, which raises another question for the ATF. If you put a pistol brace to your shoulder, does that turn your gun into something illegal?

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The ATF has gone back and forth on its answer. The agency has issued several open letters, which are not law but indications of how the agency plans to interpret the law.

In 2012, the ATF issued a letter saying braces could be attached to a pistol without turning the weapon into a short-barreled rifle.

In 2015, the agency said firing a pistol from the shoulder with a brace would not constitute a "redesign" and would require all the necessary paperwork and taxes.

When brace manufacturers sought more clarification, the ATF again appeared to change its stance in 2017. The ATF said "incidental, sporadic, or situation ‘use’ of an arm-brace" from the shoulder did not constitute a redesign, but taking "affirmative steps to configure the device" as a shoulder stock would, such as removing straps intended to wrap around the arm.

Dean Rieck, the executive director of the Buckeye Firearm Association, said trying to ban firearm components will not prevent the next mass shooting.

"After every shooting, we see the same pattern," Rieck said. "People have certain pet laws they want to see passed. You'll probably see various laws proposed."

In terms of pistol braces, Rieck said: "Things like that don't really make a difference. If your purpose is to harm people, that configuration is not ideal anyway."

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After the Las Vegas mass shooting, Cincinnati and Columbus attempted to ban bump stocks, which can increase the rate of fire of a rifle. Rieck's association successfully blocked the bans by invoking Ohio's preemption rule, which stops cities from overriding state gun laws.

Chief Biehl has not said it he believes the short barrel and pistol brace assisted Betts in the killings, but he did take a stance on the level of firepower used in the attack.

Asked about the 100-round magazines, he said: "It’s problematic. It is fundamentally problematic. To have that level of weaponry in a civilian environment unregulated is problematic."

Follow Cameron Knight on Twitter: @ckpj99