When I click this part why am I not Destroyed?

local Target = script.Parent 
function onClick(Brick)
	local Player = Brick.Parent:findFirstChild("Humanoid")
	if (Player ~= nil) then
		Player.Health = Player.Health - 100
	end
end
Target.ClickDetector.MouseClick:connect(onClick)

Use this instead.

local Target = script.Parent
function onClick(Brick)
local h = Brick.Parent:findFirstChild("Humanoid")
if(h~=nil)then
h.Health = 0
end
end
Target.ClickDetector.MouseClick:connect(onClick)

Hex's code had a minor error, he used "FindFirstChild" instead of "findFirstChild" and also you can change the local"h" to whatever you desire.