Early on the morning of September 2, 2024, a Chicago Transit Authority Blue Line train was the scene of a random and horrific mass shooting. Four people were shot and killed on a westbound train as it approached the suburb of Forest Park. The police swiftly activated a digital dragnet-a surveillance network that connects thousands...

This is today's edition ofThe Download,our weekday newsletter that provides a daily dose of what's going on in the world of technology. Inside Chicago's surveillance panopticon Chicago has tens of thousands of surveillance cameras-up to 45,000, by some estimates. That's among the highest numbers per capita in the US. Chicago boasts one of the largest...