Big Data and Mass Shootings

As always, the dots are connected after the fact, when the connecting is easy. He was booted from the military after a single month for attempting suicide. His mother advertised in numerous social-media posts his mental problems and fascination with guns. He posted his own threat on a chat site used by insecure young men, warning that students in the “northwest” should avoid school the next day.

With the usual upturned hands, experts in the aftermath tell us that “tens of thousands of people” exhibit the social isolation...