David Olofson owned what he thought to be a normal AR15. Unfortunately his AR15 as many do, misfired and shot off a three round burst. The NFA has no intent required and as such David was in the illegal possession of Machine Gun. He was arrested, convicted and his appeal was denied. He is now in prison serving 30 months. I guess he is lucky in that he was not fined nor did he receive the 10 years that the NFA authorizes.
If anyone thinks that BATFE will ignore improper transfers or possessions of items restricted by the NFA, they need look no farther than at his case outcome. For complete information on this issue and all transcripts, an interview from prison, and how the ATF appears to have framed David check out the JPFO website.