It appears the killer in this situation broke several laws.  What makes you think more laws would have prevented this?  If someone is hell bent on killing a bunch of people, then they will kill a bunch of people. Although this was a horrible thing that happened, we need to keep it in perspective.  The media likes to play on our fears.  In Chicago this year alone over 1000 people have been shot and more than 700 have died from shootings.  The majority of these shootings in Chicago are from hand guns.  In 2017 under 100 people have died from mass shootings.  So if you do the math, 7 x more people in Chicago have died from HAND gun violence than from mass shootings and this is just ONE city in the US.  If it was about keeping people safe, the Left would go after hand guns, not "assault" weapons.