On April 16, 2013, snipers fired for 19 minutes on PG&E Corp.'s Metcalf electric power transmission station near San Diego, California, knocking out 17 giant transformers that supply electricity to Silicon Valley. At least 100 rounds were fired from at least one high-powered rifle. The power grid was rerouted to avoid a blackout, but it took 27 days to make repairs and get the substation back up and running.
The incident got the attention of regulators and security professionals in the utility industry. There are some theories the...