Hansen was last seen in Phoenix, Arizona on November 10, 1995. His Centennial Middle School classes were canceled due to Veteran's Day, but he didn't tell his mother; instead, he left home as if to go to school and rode his mountain bike to visit a 13-year-old friend and classmate, Jeremy Bach, at Bach's home at Ahwatukee Custom Estates in the 3200 block of east Piro Street. Hansen's mother later realized it was a school holiday and she paged him to find out where he was. He never answered the page and he wasn't at home when she returned from work. She reported him missing that evening.

When questioned about Hansen's disappearance, Bach said they had been playing with guns and Hansen accidentally fired a shot into the wall, then panicked and fled on his bike. Hansen's case was classified as a runaway for the next two months, until sanitation workers noticed bloodstains on the top and sides of the Bach family's trash container. Investigators subsequently found two inches of blood and body fluids in the bottom of the container, as well as bloodstains in Bach's kitchen.

When confronted with the evidence, Bach admitted he'd shot Hansen in the chest and put his body in the trash container, which was then taken to the Butterfield Station Landfill. Bach said the shooting was an accident. He told several different stories about how the accident supposedly happened. Authorities launched a two-month search of the landfill at the cost of $100,000, but found no evidence.

Investigators didn't believe Bach's story and theorized he killed Hansen during an argument over a girl they had both dated. He admitted that he never tried to summon help after the shooting and Hansen took over an hour to die. In February 1996, He was charged with murder. He would become the youngest person to face trial as an adult in Arizona. The alleged murder weapon belonged to Bach's stepfather, and Hansen's parents sued him, alleging that he hadn't stored his firearms properly and may have helped Bach dispose of the body. The case was settled out of court. In January 1998, Bach was convicted of second-degree murder and sentenced to the maximum term of 22 years in prison.

Hansen's body has never been found.