Law enforcement officers tracked Hickman throughout the Pacific Northwest over several days, relying on sightings in Albany and Portland, Oregon, and Seattle, Washington, where he paid shop-owners with gold certificates given to him in the ransom.

[2] She had a twin sister, Marjorie, and one older brother, Perry Jr.[5] Parker went missing from Mount Vernon Junior High School, located in the Lafayette Square section of Los Angeles, on December 15, 1927.

The next day, December 16, the first of several ransom letters were delivered via telegram to the Parker home, demanding $1,500 (equivalent to $26,616 in 2023) in $20 gold certificates.

"[7] The first telegram, addressed from Pasadena, read, "Do positively nothing till you receive special delivery letter," with what appeared to be Marion's signature on it.

[8] Prior to departing, he recorded the serial numbers of each of the bills so they could be identified when used in future exchanges, allowing authorities to track the kidnapper.

"[14] On the evening of December 17, Perry received several phone calls at his home from the kidnapper, which established a new meeting for delivering the ransom money,[11] with the agreed location being the corner of West 5th Street and South Manhattan Place in central Los Angeles.

[17] The suspect, driving a Chrysler coupe, pulled up next to Perry's vehicle and held him at gunpoint with a sawed-off shotgun; the unknown man had a bandana covering most of his face.

[17] As soon as the money was handed over, the assailant put his vehicle into gear, moving forward, and pushed Marion's body out of the car before speeding away.

[23] Several suspects were considered at this time, including Earl Smith, the son of a local dentist; and Lewis H. Wyatt, who was apprehended and interviewed in Las Vegas, Nevada.

[25] Police traced a laundry mark on the towel found stuffed inside Marion's torso to the Bellevue Arms apartments (34°03′58″N 118°15′06″W / 34.066060°N 118.251670°W / 34.066060; -118.251670),[26] where they interviewed a number of tenants.

[23] On December 20, the fingerprints taken from the getaway car were identified as belonging to William Edward Hickman (born February 1, 1908), a former coworker of Perry Parker.

[29] He was convicted and sentenced to probation,[29] after which he spent six months living with family in Kansas City, Missouri, before returning to Los Angeles.

[27] Identifying Hickman as the prime suspect in Parker's murder, law enforcement traced his path north as he fled to Oregon.

[33] He was sighted by a gas station attendant in Albany, Oregon, on the morning of December 20, 1927, driving a green Hudson vehicle later determined to have been stolen in Los Angeles.

[33] The attendant reported the sighting to police the next day after reading a newspaper article indicating that Hickman was most likely driving a green Hudson.

[33] Police were subsequently able to trace him to Seattle, Washington, where he used two of the $20 gold certificates given to him as part of Perry's ransom to purchase clothes from a haberdashery on the evening of December 21.

[35] King immediately reported the sighting to police, indicating that Hickman had driven away from the service station east, in the direction of the Columbia River Gorge.

[37] At approximately 1:30 p.m. on December 22, Chief of Police Tom Gurdane and traffic officer Buck Lieuallen arrested Hickman in Echo, Oregon, after a frantic car chase.

"[36] While detained at the Umatilla County jail in Pendleton, Oregon, Hickman confessed to helping participate in Parker's kidnapping, but implicated two men—brothers Oliver and Frank Cramer—as accomplices who carried out the murder.

[35] Captain Bright of the Pendleton Police Department commented: "Hickman said the Parker girl was not killed in the Bellevue Arms apartment house.

[20] In subsequent correspondence, authorities were able to coax further details about Parker's murder, which Hickman disclosed via written confession after realizing his claims regarding the Cramer brothers had been disproven.

[45] After disarticulating her arms and legs, he proceeded to disembowel her, during which he stated the body jerked with such force that it "flew out of the tub," suggesting that she might still have been alive during the dismemberment.

[47] Later that night, realizing that Parker's father might want to physically see his daughter before paying the ransom, Hickman attempted to reconstruct and disguise Marion's body to make it appear that she was alive, leading him to adorn her with makeup and sew her eyes open with wire.

[48] Reflecting on the entire ordeal, Hickman told police: "She felt perfectly safe and the tragedy was so sudden and unexpected that I'm sure she never actually suffered through the whole affair, except for a little sobbing which she couldn't keep back for her father and mother.

[20][52] Evidence contradicting his insanity defense included testimony from prison guards at the Umatilla County jail in Oregon, who state that Hickman had asked them how he could "act crazy" during his incarceration.

[53] Dr. W. D. McCary, a Pendleton psychologist who examined Hickman in jail, observed that "his mind seemed clear," and he "told a straight, coherent story and was never at a loss for words.

[29] There is evidence that Hickman committed the murder, in part, for the notoriety it would bring him, as he divulged to one reporter that he wanted as much press coverage as was received by the high-profile killers Leopold and Loeb.

In these notes she writes that the public fascination with Hickman was not due to the heinousness of his crimes, but to his defiant attitude and his refusal to accept conventional morals.

[62] The same year, Andrew Jenkins (under the pseudonym Blind Andy) released the ballad "Little Marion Parker" as a single on Okeh Records, with the b-side "The Fate of Edward Hickman.

[63] The Reverend J. M. Gates also composed a Negro spiritual inspired by the Parker case, titled "California Kidnapping," in which he compared her abduction and murder to his family's past as slaves.