STANDISH – A 13-year-old Windham boy who had gone swimming with two companions at a Presumpscot River dam died Friday after climbing onto the roof of a powerhouse and coming in contact with electrical wires when he lowered himself onto a catwalk, authorities said.

The Cumberland County Sheriff’s Department said MacKenzie MacVane fell about 40 feet into the water and was found unconscious. He was pronounced dead after being taken to Maine Medical Center in Portland.

Authorities said the property was fenced off and posted to warn against trespassing.