If you see blackening on surfaces above the destruction, it can be caused by long burning, by smoke-soot which lasted many seconds/minutes, without any plasma-explosion.
But if you see blackening on surfaces to the side and/or below, that's caused by "metal-black," pure metal-powder which was condensed out of a blazing bright plasma of arcflash.
Didn't the electrician report a huge flash of light and a loud buzz sound? If they were burned but not electrically shocked, that was from skin contacting the plasma in the arcflash, which is usually far hotter than any flame. (The arc-plasma mostly made of metal-vapor, incandescent gas heated far above the boiling point of molten copper or aluminum.)
In your top picture, the blackening is to the side (so not caused by many minutes of rising smoke,) and it has radial lines from explosive trajectory of gas and metal particles. Almost certainly there was a large plasma (arc flash,) many inches across if not larger. Where it touched cold metal, the vaporized metal inside the flash would condense, forming pure-metal "soot."
Metal nano-powder is typically colored black. Copper, aluminum, even etc., creates a light-absorbing black soot when its particles are fine enough. No carbon needed, the black stuff is pure copper or aluminum. You can buy "platinum black" or "copper black" from chemistry suppliers, which is simply ultra-fine pure metal powder.