Hotline Miami style gun?

I want to create a gun that shoots in the style of Hotline Miami. By this, I mean a gun similar to the one in this video.

My script right now draws a ray from the gun's handle to the mouse's location. My problem is that I don't want it to follow the mouse, but continue straight in the direction the player shoots. Also, the ray shouldn't be able to move on the y axis, because then the bullet's just hit the ground.

Code

local tool = script.Parent
local player = game:GetService("Players").LocalPlayer
 
tool.Equipped:connect(function(mouse)
	print("Tool equipped!")
 
	mouse.Button1Down:connect(function()
		print("Mouse pressed!")
		local ray = Ray.new(tool.Handle.CFrame.p, (mouse.Hit.p - tool.Handle.CFrame.p).unit * 300)
		local part, position = workspace:FindPartOnRay(ray, player.Character, false, true)
 
		local beam = Instance.new("Part", workspace)
		beam.BrickColor = BrickColor.new("Ghost grey")
		beam.FormFactor = "Custom"
		beam.Material = "Neon"
		beam.Transparency = 0.25
		beam.Anchored = true
		beam.Locked = true
		beam.CanCollide = false
 
		local distance = (tool.Handle.CFrame.p - position).magnitude
		beam.Size = Vector3.new(0.2, 0.2, distance)
		beam.CFrame = CFrame.new(tool.Handle.CFrame.p, position) * CFrame.new(0, 0, -distance / 2)
 
		game:GetService("Debris"):AddItem(beam, 0.1)
 
		if part then
			local humanoid = part.Parent:FindFirstChild("Humanoid")
 
			if not humanoid then
				humanoid = part.Parent.Parent:FindFirstChild("Humanoid")
			end
 
			if humanoid then
				humanoid:TakeDamage(30)
			end
		end
	end)
end)

Thanks, -Mex