THE DANGER TO THE GRID OF sniper attacks on power substations. “The country’s roughly 2,000 very large transformers are expensive to build, often costing millions of dollars each, and hard to replace. Each is custom made and weighs up to 500,000 pounds, and ‘I can only build 10 units a month,’ said Dennis Blake, general manager of Pennsylvania Transformer in Pittsburgh, one of seven U.S. manufacturers. The utility industry keeps some spares on hand.”

If the D.C. sniper had known about this, he could have produced a lot more chaos.