An April 16, 2013, attack had been virtually unreported until the The Wall Street Journal reported it yesterday. It started when someone (or some ones) entered an underground vault to cut telephone cables, and then fired more than 100 shots into PG&E’s Metcalf transmission substation (near San Jose) knocking out 17 transformers. Electric officials were able to avert a blackout, but it took 27 days to repair the damage.

The attack was “the most significant incident of domestic terrorism involving the grid that has ever occurred” in the U.S., said Jon Wellinghoff, who was chairman of the Federal Energy Regulatory Commission at the time.

Wellinghoff who stepped down in November, apparently gave high-level briefings to federal agencies, Congress and the White House last year. But because nothing has happened to capture the perpetrators or better safeguard the power grid, he went public with it now.