In school we had a public display exhibition - a series of  LEDs mounted on PCBs with shifters. Like, you put in a color at the first PCB and pressed the &quot;shift&quot; button and the color would shift through the chain, the color of the last PCB in the chain would vanish. Each PCB had a capacitor on the 12V supply rail.<p>So, I needed to swap the PSU because we planned to add more of them, and I plugged it out - and cut the supply cable with a scissor. Twelve capacitors blew out (I believe because the ICs turned off the power of the LEDs before the caps were discharged, they were ridiculously huge anyways)... right in the middle of school day, and a week before there was some retard running amok and killing students.<p>tl; dr: Shorted 12 caps, huge explosion sound, peoples panicked and thought of a school shooting.