The 21-year-old woman's remains were found on Larch Mountain late Friday around the same time police arrested Jonathan Holt.
A tip led police to 24-year-old Holt, who lived in Heichel's apartment complex, and was an acquaintance of the victim and her husband, according to Gresham Police Chief Craig Junginger.
A police interview of Holt revealed inconsistencies, the chief said, and forensic evidence tied him to the victim's car. Investigators had obtained Holt's fingerprints and DNA.
When Holt voluntarily reported to an additional interview Friday evening, police had just located the victim's body. He was placed under arrest a short time later.
The Starbucks barista reportedly left her apartment for work at about 6:45 a.m. Tuesday on a drive that typically takes less than five minutes.
Her husband called police roughly three hours later. He told investigators he tried to reach his wife multiple times after her boss alerted him that she never arrived for her 7 a.m. shift.
Police said Heichel's ATM card was used at a nearby Troutdale gas station at 9:14 a.m. Tuesday. Two hours later, her sport utility vehicle was found in a Walmart parking lot with the passenger side window smashed.
A child later found her cell phone in a field that lies between the gas station and the Walmart, giving investigators another venue to search.
News of the major break in the case ended an emotional week of uncertainty for the victim's family and friends.
"Words can't begin to express the sadness that our family is experiencing tonight," said family spokesman Jim Vaughn. "This has been the most traumatic thing that has happened to us, not only as Whitney's family, but her spiritual family as well, because we are so close."
Greshsam Mayor Shane Bemis said the entire city had been "shaken to the core" by the tragedy.
"To say that this case brought fear and anxiety to the community is a vast understatement," he said. "Whitney, in many ways, represented our daughters, our wives, sisters, friends and loved ones."