When the assault weapons ban expired in 2004, there was an almost immediate and steep rise in mass shooting deaths in the years that followed.
Experts say white supremacists, much like jihadists, are radicalized through the internet.
The Massachusetts senator is also leading in Iowa where the Democratic primaries will kick off next year.
Trump blamed video games and mental illness for the shooting but failed to present a plan for gun control in the U.S.
Democratic nominee hopefuls call for change and blame Trump’s racist rhetoric after 20 shot dead in El Paso.