How do I get the rest of a string after a sequence?

What I need is help getting the end of a string, in my script when a player uses a pattern in the chat it shows the player's name and the message after the pattern, the problem is that it only shows the name and not the pattern after the sequence. Here is the script I am using:

local admins={"ultrabug", "FredeyFly"}
game.Players.PlayerAdded:connect(function(np)
    for i,v in pairs(admins) do
        if np.Name==v then
            np.Chatted:connect(function(msg)
                if string.sub(msg, 1, 2)=="m/"then
                    cmt=np.Name..": "string.sub(msg, 3)
                    cm(cmt)
                elseif string.sub(msg, 1, 5)=="kill/"then
                    plr=game.Players:findFirstChild(string.lower(string.sub(msg, 6)))
                    if plr ~=nil then
                        Kill(plr)
                    end 
                end
            end)
        end
    end
end)
function cm(text)
    local label=Instance.new("TextLabel")
    local sg=Instance.new("ScreenGui")
    for a,b in pairs(game.Players:GetChildren())do
        plabel=label:Clone()
        psg=sg:Clone()
        psg.Parent=b.PlayerGui
        plabel.Parent=psg
        plabel.Size=UDim2.new(1, 0, 1, 0)
        plabel.Text=text
        plabel.BackgroundColor3=Color3.new(0, 0, 0)
        plabel.BorderColor3=Color3.new(255, 0, 0)
        plabel.TextColor3=Color3.new(255, 0, 0)
        plabel.TextScaled=true
        plabel.BackgroundTransparency=0.5
        wait(6)
        psg:Destroy()
    end
    label:Destroy()
    sg:Destroy()
end
function Kill(player)
    player.Character.Humanoid.Health=0
end