While attending the University of Wisconsin–Stout and living in an apartment in Menomonie, Wisconsin, Helder planned to plant pipe bombs in mailboxes across the United States to create a smiley face shape on the United States map. The bombs, which were packed with BBs and nails, were rigged to explode as the mailboxes were opened. Completed and rigged bombs were found in Nebraska, Colorado, Texas, Illinois and Iowa. In Iowa, six people, including four mail carriers, were injured when the bombs detonated. Ultimately, Helder planted 18 bombs and covered 3,200 miles. He was eventually captured in rural Nevada before he managed to complete the full smile. At the time of his arrest, police were looking for an unknown suspect driving a black Honda Accord and newspapers reported that he was wearing a Kurt Cobain T-shirt. The bombings were heavily covered by the United States media.
While Helder was not at the top of his college class, his teachers described him as a reasonably good, quiet and polite student and at first there was confusion as to what the motivation for the bombings could be. Within the year prior to his arrest, Helder had become passionate about astral projection techniques and came to believe that death of the flesh and body is not the end of existence, as evidenced by the manifesto he sent to The Badger Herald of the University of Wisconsin–Madison at the beginning of the bombing spree. The essay also includes statements such as
I'm taking very drastic measure in attempt to provide this information to you... I will die/change in the end for this, but that's ok, hahaha paradise awaits! I'm dismissing a few individuals from reality, to change all of you for the better"
and ends with the words "written before any of the bombs".
It later came to light that his actions were an attempt to garner media attention so that he could spread a message denouncing government control over daily lives and the illegality of marijuana as well as promoting astral projection as a method to reach a higher level of consciousness.
In April 2004, a federal judge found Helder incompetent to stand trial. While the judge could free Helder if doctors find he is not a threat to society, legal experts doubt this possibility due to the violent nature of his crimes. He has been diagnosed with schizoaffective disorder and remains incarcerated in the Federal Medical Center in Rochester, Minnesota.
Prior to his bombing spree, Helder was a member of a Rochester, Minnesota, three-piece grunge band named Apathy. Although the band was successful only on a local scale, it recorded a CD named Sacks of People at the end of their first summer together, which they funded and released themselves.
When the news broke that Helder was the pipe bomber, the media made significant mention of his status as a musician. Many music critics scrambled to acquire copies of Apathy's CD, some of which were auctioned on eBay for as much as $200.