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Police are asking for the public’s help as they search for a missing 18-year-old man from Sylmar whose phone was located with the help of an app near Mount Wilson area on Tuesday, the same day a brush fire charred dozens of acres in the area.

Matthew Huerta was last spotted around 11:30 p.m. Monday in the 13400 block of Bradley Avenue, according to the Los Angeles Police Department.

Elaine Morelos, Huerta’s sister, told KTLA her younger brother had left the family’s home around 4:30 a.m. or 5 a.m. Tuesday — presumably to go jogging, as he usually does around that time.

Huerta never returned, however, prompting concern from the tight-knit family, and they immediately began trying to locate him.

They found a letter indicating the teen was thinking of hurting himself, and that he was experiencing depression and mental health issues, according to Morelos.

With the help of the Find My Friends app, Huerta’s friends were able to trace his cellphone to the Mount Wilson area, near where the fire broke out on Tuesday, she said.

Family and friends were originally unable to access the area as crews battled a 50-acre brush fire that continued to burn Wednesday.

Morelos issued a desperate plea to her brother, as well as to those who may have seen him since his disappearance.

“If he’s out there, if he’s scared, we just want to let him know we’re all waiting for him. If anybody has seen him – I mean, we’re hoping he’s scared to come home. We just want him home,” said Morelos, who is a former KTLA employee.

Huerta’s phone is still ringing, and texts appear to be going through to his phone, leading Morelos to believe he may have left the device in his vehicle.

“There’s indication, according to my father, that sheriffs saw someone exiting a white car matching his 2012 Nissan Sentra,” she said, referring to surveillance video. “But they didn’t see that person walk back.”

Authorities are aware that he is missing, and are searching the area, including in abandoned buildings, Morelos added.

She described her brother, the youngest of six siblings, as a “normal, happy kid,” who played soccer and had just started college at Cal State Northridge University.

“I’m desperate at this point, we don’t know what to do,” Morelos said.

Huerta is described as Hispanic, with brown hair and brown eyes, standing 5 feet 11 inches, and weighing about 140 pounds, according to an LAPD news release.  He was wearing a white T-shirt, black pants and a black baseball hat when he was last seen.

Anyone with information about his whereabouts is urged to call Officer Garcia or Detective Palmer of LAPD’s Missing Person Unit at 213-996-1800. During non-business hours and weekends, callers should dial 1-877-527-3247.

Anonymous tips can also be left by calling L.A. Regional Crime Stoppers at 1-800-222-8477.