Whenever we have a "mass shooting," the liberal establishment calls for tougher gun control laws. Likewise, the DOJ announces an investigation.
i) To begin with, people fixate on numerically clustered violence, but that's often artificial. If you have 20 people shot on one day in one place, that's a huge news item. But if you have one person killed per day over a 20-day span in the very same city, that's buried in the back pages of the newspaper. Even though the totals may be the same, we tend to hype clustered totals. The same number spread out over days doesn't garner the same attention.
ii) Because the liberal establishment cannot or will not solve the real problem, it diverts attention to a decoy issue. For instance, there's clearly a correlation between global warming rhetoric and ecoterrorism, but the liberal establishment doesn't demand that we crack down on Al Gore.
The liberal establishment is in denial about the manifest link between Islam and terrorism, so it must deflect attention away from its failure to address the real problem.
Likewise, some shooters suffer from mental illness, but there's no convenient solution for that. If you make involuntary commitment easier, that will lead to predictable abuses.
iii) There is, though, a more sinister element to this. There's a sense in which mass shootings further the liberal agenda. Mass shootings are pretext for greater domestic surveillance, a pretext to expand law enforcement, a pretext to disarm the public. It empowers the bureaucracy. Liberal officials have a totalitarian impulse. They don't want freedom. They have a utopian vision that requires both massive and minute social control.
They're spoiling for an excuse to declare martial law. And we've come close to that. Consider the city-wide lockdown after the Boston Marathon bombings. Although I don't think the authorities instigate these crimes, our immigration policy on Muslims has the same effect.