The boy looks serious despite his bright red shirt and the picture of a monster truck on his chest.
Albuquerque, N.M., police hope that the composite sketch of the unidentified boy will trigger someone's memory and help police find who buried the child in the sand under the swing set in a city park.
"We've got high hopes it will trigger someone's memory of this child," said Officer John Walsh, an Albuquerque police spokesman.
"We have high, high hopes that that single tip's going to lead us to the family" who used Alvarado Park as a grave for a little boy.
Releasing the sketch was the latest effort to solve the mystery of the boy who has been dubbed "Baby Justice" and "Baby Angel."
On Tuesday, police released photos of the boy's sneakers and T-shirt, and Walsh said the 50 investigators assigned to the case have received about 100 tips so far.
The National Center for Missing and Exploited Children is helping the department, he said.
Albuquerque Police Officer Nadine Hamby told ABCNews.com that, based a preliminary, partial autopsy, the child was either 3 or 4 years old, weighed 38 pounds, was 38 inches tall, and was of either American Indian or Hispanic descent.
He had no visible scars and had quarter-inch length brown hair and brown eyes. Other than the tiny black Skechers sneakers, the little boy was wearing black jogging pants and a red T-shirt with a picture of a monster truck.
There are no children matching his description reported missing in the area, Hamby said, leading police to believe that whoever buried him in the sand is either his caretaker or otherwise close to him.
Hamby said a local mother -- whose name has not yet been released -- was at Alvarado Park with her two children. As one of her children was playing on the swings, the back-and-forth motion disturbed the sand underneath, revealing a tiny black Skecher sneaker with gray and lime-green designs on it.
Hamby said the woman grabbed the sneaker to move it out of the way, figuring another child had left it behind, "and sees that it's connected to a leg -- at least an ankle."
Hamby said the mother dropped the foot and called police, who unearthed the rest of the body. The medical examiner, she said, determined the boy had been underneath the playground for no more than 48 hours.
Grieving for 'Baby Justice'
Hamby said police have no reason to believe the boy is not from the Albuquerque area but are keeping all options open until they hit on a lead that will help identify him.
Hamby said police are checking every possible place the child could have come from, including day care centers and nurseries.
"We went to the homeless shelters just to rule out people who were traveling through," she said, adding that all known sex offenders have been accounted for.
The National Center for Missing and Exploited Children ran a search of all missing children nationwide, Hamby said, and none matched their little boy's description.
At the playground, a makeshift memorial with flowers, toys and balloons has been growing as parents gather to talk about the mystery.