https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwir3P-J5frWAhUX8GMKHYZwD10QqUMIMjAC&url=http%3A%2F%2Fwww.recordonline.com%2Fzz%2Fnews%2F20171016%2Fwhy-unknown-motive-in-las-vegas-massacre-is-so-unsettling&usg=AOvVaw3cBahJUz0DGChqBQ8Wh6j3
That article hits precisely where the apparent lack of motive will predictably hit. Not being able to rationalize even the most irrational motive, in a vacuum, people will turn on the device used rather than the motivating sickness of the one who used it. Predictably, this will be a push to feel safe in an uncertain world, which is part and parcel of the whole illicit rationale used to push gun control.
Actually discerning and providing a motive, be that Islamism or other terrorist motivation, organic or illness-induced mental problems, psychological problems, medication side effects, being p.o.-ed at country music fans, sleep deprivation, clinical depression, whatever the thing that led to this, it would give people a way to understand, to feel they could somehow avoid or protect against being caught up in another incident, or reason to believe such could be prevented.
Without that reassurance that this was an act which, no matter how difficult, can be understood in the sense that there was some cause, the vitriol, the onus will fall on the tools he used rather than the cause, the individual. Even the NRA is falling into the trap of blaming the device and not the user when it calls for the reevaluation of slide (bump) fire stocks.
It is the emotional trap that people fall into when logic fails, and logic isn't being given much to chew on.