Conspiracy Theories In the Wake of Tragedies

Conspiracy theories have been bouncing around in the wake of the shootings in Orlando: There was more than one shooter. There’s video of the attack and the FBI won’t release it. President Obama was in on it. Or the most unkind and absurd, that the massacre was faked. Similar claims were made after the mass shootings at Sandy Hook in 2012 and Isla Vista two years later. Where do these conspiracy theories come from, and why do people buy into them after mass shootings?