Michella and her two younger sisters were visiting Puget Park, in Tacoma, Washington on March 26, 1986, when Michella left on her bicycle at about 10 a.m. to get lunch for her sisters. Meanwhile, her sisters left the playground area to play near a gulch. When they returned, Michella’s bicycle was at the playground area and sandwiches were waiting for them on the picnic table, but the sisters could not find Michella. She was reported missing to the local police.

The police responded and searched as well. Eventually a search and rescue unit found Michella’s body in an isolated area of the gulch more than a quarter mile away from the play area of the park. The Medical Examiner conducted an autopsy and determined that Michella died from blunt force trauma to the head. There was also evidence of sexual assault.

In 2006, a male DNA profile was developed from the swabs collected at the autopsy. Detectives searched state and national data bases but did not find any matches to the profile.

In February 2017, then Tacoma police detective Lindsey Wade began working with investigative genetic genealogist Barbara Rae-Venter. A DNA SNP profile was generated by FTDNA and uploaded to FTDNA and GEDmatch. Using Investigative Genetic Genealogy Barbara and Nancy Averill identified two Hartman brothers and two of their cousins as suspects. The Hartman brothers both lived in the north end of Tacoma during 1986. Barbara and Nancy asked to remain anonymous in any press releases.

In 2018, following identification of the Golden State Killer by Barbara Rae-Venter working with the FBI, Parabon Nanolabs began contacting agencies for whom they had performed their Snapshot analysis. Tacoma PD had been one of their customers several years previously and upon learning that Tacoma PD already had some suspect names offered to do a free "second opinion". Parabon also identified the Hartman brothers as suspects.

Gary C Hartman was put under surveillance. He was observed using a napkin at a restaurant. The napkin was collected by the detective who was surveilling him. The napkin was submitted to the state crime laboratory for DNA extraction and preparation of an STR profile. This profile was compared with the profile developed from the crime scene DNA and was a match. Hartman was arrested on June 22, 2018 and charged with first-degree murder and first-degree rape of Michella Welch.