Could it be that the kid was dropping rocks in the river in the late afternoon (the article didn't say what time of day it happened) and when it started getting dark a photocell or timer kicked in turning the power on to the lights? And thus the kid suddenly gets zapped? And the city workers checked the bridge during the daytime when the photocell has the lights off and find no voltage? Maybe a fault in the wiring downstream of the photocell (either a frayed wire in the pole, or maybe a fault in the ballast of the streetlight itself)?
