A Democratic senator responded to the Sunday mass shooting at a Texas church by suggesting the U.S. adopt a law that is already on the books.

Hawaii Sen. Brian Schatz (D.) shared an excerpt of a New York Times story detailing how, while in the military, the shooter was convicted of assaulting his wife and infant step-son.

"A simple idea: Anyone convicted of domestic abuse should see their rights under the 2nd Amendment severely curtailed," Schatz tweeted on Monday.

A simple idea: Anyone convicted of domestic abuse should see their rights under the 2nd Amendment severely curtailed. https://t.co/bsyihrklJf — Brian Schatz (@brianschatz) November 6, 2017

In fact, federal law already prohibits domestic abusers from purchasing or owning guns.

Passed unanimously by Congress in 1996, the Domestic Violence Offender Gun Ban prevents anyone who has been convicted of misdemeanor domestic abuse, or anyone subject to a domestic violence protective order, from owning a weapon.

The Supreme Court upheld the constitutionality of the law in 2016, ruling 6-2 that it did not matter if the person convicted of domestic abuse committed their actions recklessly or unknowingly.

While in theory the killer should have been banned from owning guns, NPR reports the Air Force mistakenly neglected to enter his conviction into the federal database that would have prevented him from purchasing a gun.