User blog comment:AMarbleHornet/Who is sesseur?/@comment-25148755-20151004232909

The history of JtK (paraphrased from searching on Google):

The famous picture shows up in a video posted by sesseur titled Jeff the Killer [Original story] in 2008. It's short (about 2:30) and pretty terrible (the pic is slightly creepy). It says Jeff was burned by acid when tryi to clean his bathroom. His brother Liu is introduced. Based on pics of Jeff (preburning) and Liu they appear about college aged.

The picture shows up again when a user named killerjeff starts posti on the site Newsground as the character from the video. The picture is eventually identified by reddit users as a highly photoshopped version of a Katy Robinson, supposedly a girl driven to suicide after she was internet bullied on 4chan forums.

The actual story we think of as Jeff the Killer (the bullies, the bleach etc) came sometime after that. The author is, as far as I can tell, unknown.