Command kill in command blocks doesn't work 100% correct

I create a tramp to protect my chests with important things, that tramp has a command block with this command: /kill @e[r=5], but, when i put a redstone wire activated in one side, the command block didn't kill me and i was above the command block, i tried with levers, buttons, pressure plates, redstone torchs, etc. I nedd that command working 100% fast, because in this moment i gonna put my world in multiplayer and someone can stole my things in that chest