A California man pleaded guilty Friday to charges that he shut down the data center responsible for managing the state's electrical supply.

Lonnie Denison, 33, is now facing as much as five years in prison and a US$250,000 fine after admitting to breaking a glass cover and hitting the emergency "off" switch at the California Independent System Operator (Cal-ISO) data center in Folsom, California, on April 15. By doing so, he shut off the power in the data center. He was formerly a contract Unix system administrator at the center.

Cal-ISO is the nonprofit organization that manages California's power. By knocking these systems offline, Denison effectively cut the state off from the energy market, leaving California vulnerable to blackout conditions. No blackouts occurred, however, because the data center went down at 11:23 p.m. on a Sunday -- a time when electricity demand is typically at a lull. "If this deliberate shut-off had occurred in the morning ... things would have been far more severe," wrote Matthew Amant, the California Highway Patrol officer assigned to investigate the incident, in an affidavit.

It's not clear why Denison would have wanted to flip the switch on California's power, but according to U.S. attorneys, he was in a dispute with co-workers and just minutes before the incident had discovered that his computer privileges had been revoked.

Prosecutors allege that he followed up the power outage by sending an e-mail bomb threat the next day to an unnamed Cal-ISO employee, saying, "Hey, at one point I respected you ... you have a new kid. So this is only because of him. Get out before the timer expires. Not long now. Take care."

Following this threat, Cal-ISO evacuated about 500 employees from all three of its Folsom campus buildings, transferring control of the grid to a second control center.

That same day Denison spoke with a friend, admitting that he had tried to "shut off the power grid," according to a statement from the U.S. Department of Justice.

The Sunday night incident knocked the data center down for about two hours, but it took 20 computer technicians about seven hours to fully restore the system. The total cost of the outage is estimated at $14,000.

Denison, of Sacramento, California, is set to be sentenced on Feb. 29, 2008, in federal court.