Around 1:00 AM on April 16, at least one individual (possibly two) entered two different manholes at the PG&E Metcalf power substation, southeast of San Jose, and cut fiber cables in the area around the substation. That knocked out some local 911 services, landline service to the substation, and cell phone service in the area, a senior U.S. intelligence official told Foreign Policy. The intruder(s) then fired more than 100 rounds from what two officials described as a high-powered rifle at several transformers in the facility. Ten transformers were damaged in one area of the facility, and three transformer banks — or groups of transformers — were hit in another, according to a PG&E spokesman.

Cooling oil then leaked from a transformer bank, causing the transformers to overheat and shut down. State regulators urged customers in the area to conserve energy over the following days, but there was no long-term damage reported at the facility and there were no major power outages. There were no injuries reported. That was the good news. The bad news is that officials don’t know who the shooter(s) were, and most importantly, whether further attacks are planned.

“Initially, the attack was being treated as vandalism and handled by local law enforcement,” the senior intelligence official said. “However, investigators have been quoted in the press expressing opinions that there are indications that the timing of the attacks and target selection indicate a higher level of planning and sophistication.”