Can a camera flash light near high voltage wires create medium to pass electricity? I found a story of a boy who took a picture with flash light near 40,000 voltage lines. When it flashed, current came to his camera (as a spark may be) and passed through his body making him dead.
Is it possible? Someone said that flash light can ionize the air to an extent that it can happen.
 A: NO!!!
A flash-light does not ionize the air at all.  Not only is the intensity of a flash-light very very low; but the wavelength of light needs to be lower than a certain threshold (in the ultraviolet) to ionize most substances.
The story is probably false (especially since your source is a forum); but if it is true; the discharge was most likely unrelated to the camera.
A: Actually the flash consists of a capacitor connected directly across the flash, which is not conductive until a trigger (moment of camera taking picture) is activated. This trigger making a connection between the capacitor and a high voltage transformer, ionizes the flash tube, making it conducting inside, so that the capacitor is discharged through the tube. But: the ionizing will PROBABLY not be high enough to make the air from the high voltage source conducting, making it safe to handle flashes around high voltage sources. This is merely a thesis, I have no documentation to back it up, so be safe, and try not to hurt yourself.
