Stargirl, you're a person after my own heart. "Set 'em up" nice idea. How about some of those cans of exploding snakes you get get in a "Joke / magic shop"
"Sneak" out to the rubbish can acting like you don't want to be seen, and put a box in the can. Should some "old biddy" have a heart attack, then it's just one less bothersome person to contend with.
