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!