Sure there is. The real "slippery slope propaganda" is that more gun laws could have somehow prevented this tragedy and others like it.
This young man already broke numerous laws perpetrating this PREMEDITATED crime. I challenge you to name one (rational) law that could have been passed that could have prevented him from committing this criminal act. Any law (short of confiscation and criminalization of gun ownership) could have been easily circumvented by this young man intent on completing his deadly mission.
Obviously, you have no interest in investigating the true root causes of these violent acts. That is the one, true way, to prevent these kinds of acts from ever happening again.