Cooperative Escapism in Familial Relations - S4-E5
Trivia: During the fifth episode of Season Four ("Cooperative Escapism in Familial Relations"), Dean Pelton is shown to be wearing a cowboy's outfit during one scene. This is a very close replica of the cowboy costume Jeff Winger wears in the Season One Halloween episode "Introduction to Statistics." Later, during the seventh episode of Season Four ("Economics of Marine Biology"), when Pelton's pants are pulled down, it becomes clear that he is wearing the same underpants as Jeff from the Season One episode "Physical Education." It is confirmed in the DVD commentary that these are just two of many subtle examples of Pelton emulating Jeff's style, due to Pelton's obsessive crush on Jeff.
Answer: His attempt to "kill" Jeff was to roll at him as an iPad on a stick. He knew it wouldn't work, but it played to the story that he was a killer as he knew Jeff would tell people about it, or attempt to retaliate for it.