In the early hours of 16 April 2013, one or more gunmen opened fire on the Pacific Gas & Electric (PG&E) Metcalf substation for nearly 20 minutes. They took out 17 transformers at the Silicon Valley location and then slipped away into the night before police arrived.
The attack caused significant damage but did not result in a power outage. It did, however, reignite a conversation about the physical security of the electricity grid in the United States and elsewhere, shifting the focus somewhat away from cybersecurity. The Wall Street Journal later reported that the Federal Energy Regulatory Commission (FERC) had done a study that same year assessing grid weaknesses. According to the newspaper, it found that a coordinated attack on a small, specific set of the 55 000 transmission substations in the United States could plunge the entire nation into darkness.