why does my game keep crashing when i play this script?

so ive been working on this script that when a key is pressed it fires some functions to open a aura type thing around the player and it checks the magnitude around the player for other players. if a player is in certain distance from the local player it fires a function to damage them. but when i test or play the game and test it with a alt account eh game crashes. heres the script:

local Players = game:GetService("Players")
local Player = Players.LocalPlayer
local Char = Player.Character or Player.CharacterAdded:wait()
local db = true
local onn = false

local Distance = 15


game:GetService("UserInputService").InputBegan:Connect(function(input, event)
	if input.KeyCode == Enum.KeyCode.Z and db then
		db = false
		if onn == false then
			onn = true
		elseif onn == true then
			onn = false
		end
		for _,Plr in pairs(Players:GetPlayers()) do
			if Plr ~= Player then
			    local Chr = Plr.Character
				local HRP = Chr:WaitForChild("HumanoidRootPart")
				repeat
					if HRP and Player:DistanceFromCharacter(HRP.CFrame.Position) < Distance then
						local MYHRP = script.Parent.HumanoidRootPart.CFrame.Position
						local mag = (HRP - MYHRP).Magnitude
						if mag < Distance then
							script.Parent.FireKillingIntent:FireServer(HRP)
							wait(0.5)
						end
			        	print("In Range")
					end
				until onn == false
			end
		end
		wait(0.5)
		db = true
	end
end)



game:GetService("UserInputService").InputBegan:Connect(function(input, event)
	if input.KeyCode == Enum.KeyCode.Z and db then
		db = false
		if onn == false then
			onn = true
		elseif onn == true then
			onn = false
		end
		script.Parent.OpenkillingIntent:FireServer()
		local san = game.Workspace.SAN.HumanoidRootPart
		repeat
			local HRP = Char.HumanoidRootPart.CFrame.Position
			local mag = (san.CFrame.Position - HRP).Magnitude
			if mag < Distance then
				script.Parent.FireKillingIntent:FireServer(san)
				wait(0.5)
			end
		until onn == false
		wait(0.5)
		db = true
	end
end)

the first UserInputService function is for players and the second is for a npc in workspace i used for testing. i cant even get which line im crashing on because when the game crashes i have no choice but to leave. anyway i hope somone can help me, and thank you!