On April 16 last year around 1 a.m., someone cut underground cables to knock out phone service around PG&E's Metcalf substation, just south of San Jose. According to a PG&E official, the intruder or intruders then shot out multiple transformers with a high-powered rifle.
No long-term damage or serious power outages resulted. KCBS San Francisco at the time called the incident vandalism, though it quoted one official as saying, "(I)f you want to call that sabotage, that’s what it looks like."
In December, Foreign Policy magazine upped the ante by citing California Rep. Henry Waxman's characterization of the incident:
"It is clear that the electric grid is not adequately protected from physical or cyber attacks," Waxman said. "(The San Jose incident was) an unprecedented and sophisticated attack on an electric grid substation with military-style weapons. Communications were disrupted. The attack inflicted substantial damage. It took weeks to replace the damaged parts. Under slightly different conditions, there could have been serious power outages or worse."
And today, the Wall Street Journal has gone one level of alarm further with a story about what the attack could portend. In the article, Jon Wellinghoff, chairman of the Federal Energy Regulatory Commission at the time, calls the attack "the most significant incident of domestic terrorism involving the grid that has ever occurred" in the U.S.