An apparently homeless thief was fatally electrocuted while trying to steal copper wiring from a California construction site — as power was knocked out to 2,500 homes, reports said.

The unidentified man was killed Sunday in a vacant strip mall that’s in the process of being demolished, with witnesses saying they heard a loud explosion at around 2 p.m. before electricity went out for several hours, police told CBS News.

The explosion is believed to be a transformer that blew up, knocking out power for several hours, Pomona police said.

One neighbor rushed to the scene where a woman begged him for help.

“She just kept saying, ‘Help us,’ and I was like, ‘What am I supposed to do?,'” Mykil Walker told NBC News.

A construction worker at the scene said it wasn’t the first time someone tried to nab copper from the demolition site.

“Obviously, we kick them out for security reasons and safety reasons,” Frederico Velarde told CBS. “They just keep coming back.:

The would-be thief was apparently part of a larger crew of transients that were living on the property and who had been warned about the dangers of tampering with the live wires, Velarde said.

Power had been cut above ground but the wiring underground — where the man was electrocuted — was still live, CBS reported.

The theft of copper wiring is widespread throughout Los Angeles, leaving many communities in the dark, as the valuable metal is being stolen for resale.

The Sixth Street Bridge in downtown Los Angeles had 7 miles of copper wiring stollen worth $11,000, while repairs are estimated to cost the city $2.5 million, CBS News reported.