The Santa Clara County Sheriff's Office released surveillance video depicting an April shooting targeting a PG&E substation in South San Jose. The video shows bullets hitting the fence causing sparks. The sparks can be seen at minutes 1:54, 2:07, 2:10, 2:57 and 3:01. AT&T is offering a $250,000 reward for information leading to an arrest and conviction in the case.

Initially treated as vandalism and handled by local law enforcement, an attack on a power station in California has U.S. officials stumped and concerned about the physical security of the electrical power grid.

Foreign Policy reports:

"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."

Rep. Henry Waxman, the California Democrat and ranking member of the Energy and Commerce Committee, discussed the substation attack during a hearing on regulatory issues earlier this month. Raising concerns that the electric grids are not safe from either cyber or physical attacks, he called called the shooting at the the San Jose facility "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."

"These were not amateurs taking potshots," Mark Johnson, a former vice president for transmission operations at PG&E, said last month at a conference on grid security held in Philadelphia. "My personal view is that this was a dress rehearsal" for future attacks.

The FBI has taken over the case, and a spokesman said that they still have leads they are following up on, but wouldn't give any further details. Thus far, it appears that this was an isolated incident.

In May, a man dressed all in black was seen lurking near the substation, touching off a large manhunt by Sheriff's deputies, but he was never found.

AT&T is still offering a $250,000 reward for information leading to an arrest and conviction in the case. Anyone with information for the Santa Clara County Sheriff's Office can contact investigators at 408-808-4431.