Introduction to Finality - S3-E22
Other mistake: During Leonard's "Let's Potato Chips" YouTube video during the ending credits, you can see the video reaches the end of the load/play bar (watch the circle), yet the video continues for several seconds. Once the circle reaches the end of the load/play bar, the video is over and won't continue.
Other mistake: Since Annie had completed the terrarium the group should have at least received a passing grade since the Professor made them a group of 7.
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.