Wall Full Of Writings

I was so shocked when I went to my son's room to check up on him.He was writing stuff on his wall,bad thing about it is that he was using the sharpie permanent marker.I do not know where he found the sharpie permanent marker,but seeing it made me really angry.I do not know where to start,how I am going to erase it,or if I could erase those stuff that he wrote on his bedroom wall.Well,I am just going to wait for my husband to do it because right now I am really kinda pissed.I am trying not to be mad at my son because I know he does not know what he is doing yet,he just really loves to write and write and write although he does not know what he is writing or doing just yet.