Police are now searching for the boy’s 11-year-old half-brother and their father.
The mother contacted police overnight, according to Las Vegas Metro Police Department Lt. Raymond Spencer.
The mother told police a sketch released to the media of the child found Friday morning by a hiker resembled her son, Spencer said.
The mother later positively identified the boy after detectives showed her photos of his body, according to Spencer.
A multistate Amber Alert has been issued for the half-brother, Eden Montes, who was last seen about 9 p.m. Thursday with the 8-year-old brother and their father, according to Spencer.
Police have not been in contact with the father, 37-year-old Jose Montes, according to the lieutenant, and are asking for the public’s help in locating Montes and his son.
Spencer said police want people in the Sacramento, California, area as well as southern Utah to be on the lookout for Montes and his son.
They were last seen in a 2015 white GMC truck with license plate LV U00X. The truck was towing an RV with a checkerboard pattern on the sides and rear. The truck also has a sticker with the words “Mr. Express” in the lower right corner of the rear window.
“We are doing everything that we can to locate the 11-year-old child, Eden, and we want to locate him alive,” Spencer said.
Police had originally sought the public’s help in identifying the body found by hikers Friday morning.
The boy was found lying in a forested area of Mountain Springs Trailhead near mile marker 20 on State Route 160, according to Las Vegas police. The area is about 25 miles southwest of downtown Las Vegas.
Shortly after the boy was found around 7:45 a.m. (10:45 a.m. ET) Friday, medical personnel pronounced him dead at the scene, police said.
Authorities are not releasing information about injuries to the body, Spencer said. The boy’s cause and manner of death will be released by the Clark County coroner’s office.
“The investigation conducted by LVMPD Homicide Section indicates that the victim may have been placed in the area in the last 12 hours,” the police department tweeted.
CNN’s Ray Sanchez, Danielle Sills and Holly Yan contributed to this report.