The sheriff of Moore County, North Carolina described attacks over the weekend that left 40,000 homes without power as unprecedented attacks carried out by cowards. Sheriff Ronnie Fields said two suspects used firearms to destroy equipment at two different substations Saturday night. The sheriff said the attacks were not random, and the suspects knew what they were doing.

“They pulled up, somebody did, and opened fire on the substation,” Sheriff Fields told a group of reporters at a Sunday press conference. “Same thing at the other [substation]. It was a gate. They went through the gate and got to the substation and shot it as well.”

The FBI is assisting in the investigation into the attacks, which caused millions of dollars’ worth of damage and could take days to fully repair. A county-wide curfew was put into place in Moore County which started Sunday night.

No motive has been established for the attacks. The sheriff said his deputies will investigate every avenue, including the possibility of domestic terrorism.

For years, electrical grid experts in the U.S. have been warning about attacks on the nation’s critical infrastructure. In 2014, snipers attacked a Pacific Gas and Electric Company substation near San Jose, California. A team of snipers used high-powered rifles to take out 17 giant transformers. No arrests have been made in connection to that attack.

In January 2022, a Department of Homeland Security report said, “domestic extremists have developed credible, specific plans to attack electricity infrastructure.” The grid is viewed as a target because transmission lines and substations are often in remote areas, and because outages could result in frustration and divisions within American society.

The Associated Press contributed to this report.