A few simple observations to help you understand American politics.
First, assume a spectacular crime.
Next, assume an opportunistic politician. Let's call him Stan.
When Stan responds to this crime by introducing a bill kick-punching suspects and/or criminals -- say by expanding the death penalty, abolishing the insanity defense, broadening police powers, mandating life without parole, or lowering the age of criminal responsibility -- this is known as responsive democratic action.
When Stan responds to this crime by introducing a bill opposed by powerful lobbies -- say a bill imposing higher penalties for financial mismanagement, or stricter gun-control laws -- this is called exploiting a tragedy for political gain, rushing to judgment before all the facts are in, and/or irresponsible populism.
I hope that helps!