Why is error given when trying to add to kills leaderstat?

I am making a gun that adds to your kills leaderstats when you get a kill but it gives me an error when i try to change the leaderstat and I do not know how to give a number to the kills leaderstats once the target is at 0 health

local deagle = script.Parent

deagle.Shoot.OnServerEvent:Connect(function(player,mousePos)
	local raycastParams = RaycastParams.new()
	raycastParams.FilterDescendantsInstances = {player.Character}
	raycastParams.FilterType = Enum.RaycastFilterType.Blacklist
	
	
	local raycastResult = workspace:Raycast(deagle.Handle.Position,(mousePos - deagle.Handle.Position)*2147000,raycastParams)
	
	deagle.Handle.GunShot:Play()
	if raycastResult then
		local hitPart = raycastResult.Instance
		local model = hitPart:FindFirstAncestorOfClass("Model")
		
		if model then
			if model:FindFirstChild("Humanoid") then
				model.Humanoid.Health -= 36
				if model.Humanoid.Health == 0 then
					player.leaderstats.Kills = player.leaderstats.Kills + 1
				end	
			end
		end
	end
end)