Timeline of sabotage triggering North Carolina power outage

The gun attack that crippled two power substations and knocked out electricity to tens of thousands of utility customers in Moore County, North Carolina, is being investigated as a criminal act and law enforcement, including the FBI, are working around the clock to identify suspects and determine a motive behind the sabotage.

The criminal vandalism has caused major disruptions throughout the county, including the closures of public schools and prompted officials to impose a nightly curfew.

Here is a timeline of how the crisis unfolded and the race by utility crews to repair what authorities described as "millions of dollars in damages":

Dec. 3 -- Just after 7 p.m. on Saturday, Duke Energy company, the local utility provider, responded to a failure at an electrical substation near the city of Carthage, which was soon followed by the failure of a second substation, authorities said. The incident plunged roughly 45,000 utility customers into darkness as freezing temperatures set in.

Dec. 4 -- Moore County Sheriff Ronnie Fields announces at a news conference that gunfire caused extensive damage to the two substations, describing the incident as "intentional vandalism." On Sunday afternoon, Fields says the FBI and the state Department of Public Safety were assisting in the investigation, and notes multiple shots were fired at each substation and that a gate to one of them was rammed open. A countywide state of emergency is declared and officials announce a 9 p.m. to 5 a.m. curfew would be imposed. The sheriff says investigators are looking into whether the attacks are related to protests over a Downtown Divas drag show in the Moore County city of Southern Pines Saturday night, but that no evidence had been uncovered linking the two events.

Dec. 5 -- Schools throughout Moore County are cancelled as Duke Energy officials say the damage to the substations is substantial and would take multiple days to replace equipment that was completely destroyed. The federal Department of Homeland Security and the White House announce they were monitoring the situation and providing federal assistance. Fields tells ABC News that the perpetrator or perpetrators knew exactly what they were doing and could face murder charges if someone dies as a result of the power outage. Gov. Roy Cooper says at a news conference that "this kind of attack raises a new level of threat" and that officials would begin working on ways to harden security to protect key infrastructure throughout the state.

Dec. 6 -- Schools are cancelled for the second day following a second night in which a curfew was imposed on county residents. Duke Energy says more than 35,000 customers are still without electricity.