Proponents say that red-flag laws can prevent mass shootings by taking away firearms from people who pose a threat of harm to themselves or others. The mother of the Parkland shooter, for example, reportedly went to police about his behavior, but at the time Florida didn't have a law that would let them take away his weapons (the state passed one in the wake of the shooting). Analysis by Everytown for Gun Safety of mass shootings from 2009 to 2017 found
that in 51% of incidents, the shooter showed warning signs
that they posed a danger to themselves or others before the shooting. A 2017 study of Connecticut's red-flag law found that for every 11 gun removals under the law, one suicide was averted. A 2018 study
found that Indiana's law "was associated with a 7.5% reduction in firearm suicides in the 10 years following its enactment."