A gunman who killed nine people and injured dozens more in a matter of seconds in Dayton, Ohio, legally obtained his gun and ammunition, according to police.
The speed with which he carried out the massacre drew attention not only to the firearm, but the large capacity ammunition magazines that enabled him to unload 41 rounds in 30 seconds.
Connor Betts opened fire early Sunday using a .223 caliber high-capacity rifle equipped with a 100-round drum magazine, Dayton Police Chief Richard Biehl said.
Betts had a total of 250 rounds in his possession during the shooting, raising fears about how many more lives might have been lost if officers patrolling nearby did not intervene and kill Betts as soon as they did.
Biehl called it "fundamentally problematic" for the gunman to have such a high "level of weaponry in a civilian environment, unregulated."
But only nine states have laws banning large-capacity ammunition magazines, and Ohio is not one of them.
Most states and the District of Columbia enacted those laws in response to mass shootings, said Ari Freilich, a staff attorney with Giffords Law Center to Prevent Gun Violence.
Large capacity magazines enable shooters to fire repeatedly without having to reload. They have been a recurring feature in some of the country's deadliest shootings, from Columbine High School in 1999 to Sandy Hook Elementary School in 2012 to Marjory Stoneman Douglas High School in 2018.
The brief pause in action to reload can save lives by giving bystanders or law enforcement a chance to intervene, according to the Giffords Law Center to Prevent Gun Violence.
For those who make it through background checks, limiting the amount of ammunition allowed in a magazine is the next line of defense, along with banning certain types of firearms, Freilich said.
"Restricting magazine capacity is probably the single most effective thing we can do to restrict the lethality of mass shootings," Freilich said.
The federal government banned gun owners from owning semiautomatic assault weapons and large-capacity ammunition magazines from 1994 to 2004, until the law expired and lawmakers failed to renew it. Now, they are legal in states without laws setting limits.
What constitutes a large capacity magazine varies among states. California, Connecticut, Hawaii, Maryland, Massachusetts, New Jersey, New York and the District of Columbia define it as a magazine capable of holding more than 10 rounds, according to the Giffords Center . In Colorado, it's a magazine capable of holding more than 15 rounds. Vermont law defines it as a magazine that holds more than 10 rounds for use in a long gun or more than 15 rounds for use in a handgun.