Was it just the light that stayed on or did it continuously fire the atty?
eGos are somewhat notorious for button sticks, either the light just stays on or the button sticks. Usually a quick thumbnail flick on button will stop it. Depending on where you got it and how long ago, contacting the vendor might help. Of course, you probably know all this.
By this time, if it hasn't stopped, you've taken it outdoors.