"Based upon what she was wearing, we believe it is her," Officer Darin Snapp said.
Police said they have a person in custody, but no charges have been filed yet.
Willoughby was last seen with the father of her children Sunday morning and police are questioning him. Her family said she was with her two children, ages 1 and 3.
"Everybody's been talking about the father of her two sons, but he's in custody on something completely separate. But we will definitely be talking to him, though," Snapp said.
Willoughby's family said her children's father told them that she left the children and went with someone else in another car.
"Essence does not leave her children, even while they were at daycare. She's always calling to make sure they are OK," a family friend, Terri Harrison, said.
Police made contact with the 42-year-old father of her two boys, who has a domestic violence history. The young boys are currently staying with their maternal grandparents.
Police received a ping from a cell phone, possibly belonging to Willoughby, near Interstate 435 and Truman Road and were in the area Tuesday morning investigating.
Up until the find Tuesday there was no sign of the mother, and it was the account of her 3-year-old that had police worried about the woman's safety.
Her boys were dropped off by their father's family members, and the older one had a disturbing description of when he last saw her. Police aren't releasing the details about what the toddler said to family members, but said it really helped give them information about what happened.
"We don't know where she is. The only witness, unfortunately, is her 3-year-old son," Harrison said earlier in the day Tuesday.
"I talked to her on Friday, and she was expressing some concerns about him (the father of her children) then being angry," the missing woman's grandfather, Jesse Frazier, said.
Since authorities said Monday they didn't have enough information to assign a whole squad, the young mother's family and friend spent the day passing out fliers and phone numbers in a frantic search of information that could help police take the next step.
They went door-to-door in places that made sense, stopped people on the street and flagged passing cars.
The effort yielded some useful leads for police to follow, including a car and an address where the boys' father was seen just 12 hours before the search party's arrival.
"People are opening up their doors. They are saying they recognize this girl from the neighborhood, so we are hopeful," Vonda Jackson said.
"We hope that Essence will come home and that she will be fine," Harrison said Monday.
Witnesses told police they saw Willoughby near the wooded area at 38th and Topping and their search of the area lead to the gruesome discovery.
Anyone with information to is asked to call the TIPS Hotline at 816-474-TIPS.
Copyright 2012 KCTV (Meredith Corp.) All rights reserved.
Family: Body found at 38th and Topping is that of missing momSearch for missing mother turns into homicide investigationThose who wish to make contributions to help raise funds for the family and childrenMore>>
Saturday, March 8 2014 12:05 AM EST2014-03-08 05:05:29 GMT
In an exclusive jailhouse interview with Fox 12, 17-year-old murder suspect Brett Pearson said he was on meth at the time of the shooting that killed his mother and injured his father. "None of it wasMore >
In an exclusive jailhouse interview with Fox 12, 17-year-old murder suspect Brett Pearson said he was on meth at the time of the shooting that killed his mother and injured his father. Video:Full jailhouse interviewMore >
Saturday, March 8 2014 12:43 AM EST2014-03-08 05:43:13 GMT
One click of the computer mouse apparently led to suspensions for many students at a Salem high school. They say it stems back to a Twitter post about a teacher. "It was a two second thought that gotMore >
One click of the computer mouse apparently led to suspensions for many students at a Salem high school. They say it stems back to a Twitter post about a teacher.More >
Sunday, March 9 2014 12:18 PM EDT2014-03-09 16:18:09 GMT
A missing California man who suffers from a serious medical condition may be in Portland. The Portland Police Bureau's Missing Persons Unit and the Santa Cruz County, California Sheriff's Office, areMore >
A missing California man who suffers from a serious medical condition may be in Portland. More >
Friday, March 7 2014 2:58 PM EST2014-03-07 19:58:33 GMT
Four people were arrested at a home littered with syringes in a heroin trafficking investigation in Battle Ground. The Clark-Vancouver Regional Drug Task Force and the Southwest Washington Regional SWATMore >
Four people were arrested at a home littered with syringes in a heroin trafficking investigation in Battle Ground.More >
Sunday, March 9 2014 12:18 PM EDT2014-03-09 16:18:06 GMT
A man is in critical condition after being stabbed in southwest Portland. Officers found the man on SW Naito Parkway, south of the Burnside Bridge, around 4 a.m. Saturday. Police were first called toMore >
A man is in critical condition after being stabbed in southwest Portland. Officers found the man on SW Naito Parkway, south of the Burnside Bridge, around 4 a.m. Saturday.More >
Wednesday, March 5 2014 10:11 AM EST2014-03-05 15:11:38 GMT
LOS ANGELES (KSBS/KCAL/CNN) - The Los Angeles city council has voted to ban electronic cigarettes in some areas of the city. Tuesday's vote was unanimous. The new rule changes city code to include e-cigaretteMore >
Los Angeles votes to ban the use of e-cigarettes in some public places.More >