how can I make math.random select more than 1 random thing?

The reason is for that theres only 1 player selected is because your using

math.random(1,  #people)

The '1' makes it only select one player.

I suggest using a table.

Much easyer to use. Example code :

criminals = {}

for i = 1, math.random(1, 5), 1 do

	while wait() do
		local NC = people[math.random(1, #people)]
		for _,plr in next,criminals do
			if plr ~= NC then
				table.insert(criminals, NC)
				break -- Stop the while loop
			end
		end
	end

end

So now what you can do is much MUCH more simple,

Example

for _,plr in next,criminals do
	local Character = workspace:WaitForChild(plr.Name)
	local Human = Character:WaitForChild("Humanoid")
	Humanoid.Died:connect(function()
		print(Character.Name..", died")
	end)
end