Topsy (born circa 1875, died January 4, 1903), was a domesticated elephant with the Forepaugh Circus at Coney Island's Luna Park. Because she had killed three men in as many years (including a severely abusive trainer who attempted to feed her a lit cigarette), Topsy was deemed a threat to people by her owners and killed by electrocution on January 4, 1903. Inventor Thomas Edison captured the event on film. He would release it later that year under the title Electrocuting an Elephant. Edison suggested electrocution with alternating current, which had been used for the execution of humans since 1890.
To reinforce the execution, Topsy was fed carrots laced with 460 grams of potassium cyanide before the deadly current from a 6,600-volt AC source was sent coursing through her body. She was dead in seconds. The event was witnessed by an estimated 1,500 people.
Video (not graphic): http://www.youtube.com/watch?v=RkBU3aYsf0Q