Backpack isn't a valid member of Player help?

So here i go again asking i just need to know what did i do wrong, because this is the script

local tool = script.Parent
local player = game.Players.player

tool.Equipped:connect(function(mouse) 
    print("Tool equipped!")

    	tool.Activated:Connect(function() 
        print("Mouse pressed!")
        local tool2 = game.Lighting.Revolver
        tool2:Clone().Parent = player.Backpack

        wait(0.5)

        tool:Destroy()

    end)
end)

and after i test it out it said Backpack isn't a valid member of Player (this is not local script this is normal script) i need to know why it doesn't read player's inventory.

You need to call the player correctly,, Since this is a server script, it won't be able to detect a "Local"Player, as Sinister said earlier. You'll need to call the player some other way.

There are a few ways to do this,

game.Players.PlayerAdded:Connect(function(player)

I wouldn't doubt if you've heard of "game.Players.PlayerAdded", it's very useful for server scripts, It will run the function whenever a; player is added to the game service "Players" The argument "(player)" is the, in other words, LocalPlayer you're searching for.

Another way is through RemoteEvents, I most commonly use RemoteEvents as a way to get the local player in a server script. I recommend you doing some research on RemoteEvent's, they're extremely crucial to scripting. They can be a lil' tricky at the start to understand and grasp, but once you learn how they work, and etc. I'm sure they'll make your job wayy easier!