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298 Cases Solved. Advancing justice for missing persons, unsolved homicides, unidentified and unclaimed remains.

Case Description

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Summary based on the NamUs case record (MP17184) and 1 other source
In the vast and often unforgiving landscape of the Arizona desert, the story of Leonzo Mateo unfolds, a narrative of a journey that took a desperate turn. At the age of 17, Leonzo, a young man from a Hispanic background, embarked on a perilous trek with a group, crossing the border on foot around July 20, 2012. He was last seen in the rugged terrain of the San Luis Mountains in Pima County, Arizona. Standing between 5'4' and 5'6' and weighing approximately 120 to 140 pounds, Leonzo had short black hair, very dark brown eyes, and a small, distinctive scar under his right eye that resembled a scratch about 3/8 inches long. His journey, filled with the hope of a different future, instead led him into the heart of a mystery that has now spanned over a decade.

The initial days of the group's journey are believed to have been arduous, culminating in a critical moment on or around the 23rd or 24th of July. Near San Luis, in the vicinity of highway 86 and the Tohono O'odham Reservation, the group made the difficult decision to separate. It was at this juncture that Leonzo's health began to fail. He was reportedly feeling unwell and suffering from a nosebleed, prompting the group to leave him to rest beside a tree. This decision, likely made under duress and with the hope of his recovery and a later reunion, marked the last time anyone is known to have seen Leonzo Andres Antonio Mateo. Some members of his original traveling party were later encountered by Border Patrol, but Leonzo was not among them.

The circumstances surrounding Leonzo's disappearance paint a somber picture of the risks inherent in such border crossings. Left alone and in a weakened state in a remote and challenging environment, his chances of survival were precarious. The Pima County Medical Examiner's Office took on his case, a silent acknowledgment of the grim possibilities. The official report details the heartbreaking account of him being left by the tree due to his illness. The investigation into his whereabouts has remained open, a persistent question in the files of missing persons. The overview of this case is one of a hopeful journey ending in an unresolved disappearance, a young life vanishing amidst the harsh beauty of the Arizona borderlands, leaving behind only questions and the enduring pain of a family left without answers.

Last Seen: Jul 20, 2012

Links to Additional Sources (1)

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Possible Unidentified Matches (10)

Unidentified remains cases whose details are consistent with this person, ranked by how closely they compare. Fields that are unknown in either case are left out of the score.

85%Strong
John Doe — Queenswell, Arizona - unidentified case UP10653
John Doe — Queenswell, Arizona
UP10653 • Found Jun 23, 2012
View case
Sex ✓Male
Age 100%Est. 15–19 vs 17
Race 100%Hispanic
Location 88%52 mi away, same county
TimingFound same day as last seen
Height 100%5'6" vs 5'4"–5'6"
Weight 89%100 lb vs 120–140 lb
Hair 100%Black vs Black
Eyes 90%Brown vs Black
83%Moderate
John Doe — northeast of Sasabe, Arizona - unidentified case UP52993
John Doe — northeast of Sasabe, Arizona
UP52993 • Found Aug 7, 2017
View case
Sex ✓Male
Age 100%Est. 20–25 vs 17 when missing
Race 100%Hispanic
Location 100%10 mi away, same county
TimingFound 5 years after last seen
Height 100%5'3" vs 5'4"–5'6"
Hair 100%Black vs Black
83%Moderate
John Doe — South Tucson, Arizona - unidentified case UP12008
John Doe — South Tucson, Arizona
UP12008 • Found May 9, 2013
View case
Sex ✓Male
Age 85%Est. 18–35 vs 17
Race 100%Hispanic
Location 89%51 mi away, same county
TimingFound 10 months after last seen
Height 100%5'4" vs 5'4"–5'6"
Weight 100%133 lb vs 120–140 lb
Hair 100%Black vs Black
Eyes 90%Brown vs Black
82%Moderate
John Doe — Near Kupk Village, Arizona - unidentified case UP16418
John Doe — Near Kupk Village, Arizona
UP16418 • Found May 15, 2016
View case
Sex ✓Male
Age 100%Est. 16–21 vs 17 when missing
Race 100%Hispanic
Location 88%56 mi away, same county
TimingFound 4 years after last seen
Height 100%5'6" vs 5'4"–5'6"
Hair 100%Black vs Black
Eyes 90%Brown vs Black
81%Moderate
John Doe — Arizona - unidentified case UP13815
John Doe — Arizona
UP13815 • Found Sep 13, 2014
View case
Sex ✓Male
Age 100%Est. 16–20 vs 17 when missing
Race 100%Hispanic
Location 92%40 mi away, same county
TimingFound 2 years after last seen
Height 100%5'7" vs 5'4"–5'6"
81%Moderate
John Doe — Itak, Arizona - unidentified case UP13748
John Doe — Itak, Arizona
UP13748 • Found Aug 5, 2014
View case
Sex ✓Male
Age 100%Est. 18–23 vs 17 when missing
Race 100%Hispanic
Location 92%39 mi away, same county
TimingFound 2 years after last seen
Height 84%5'2" vs 5'4"–5'6"
Hair 100%Black vs Black
81%Moderate
John Doe — Sasabe, Arizona - unidentified case UP13814
John Doe — Sasabe, Arizona
UP13814 • Found Jul 24, 2014
View case
Sex ✓Male
Age 100%Est. 15–25 vs 17 when missing
Race 100%Hispanic
Location 100%10 mi away, same county
TimingFound 2 years after last seen
Height 84%5'8" vs 5'4"–5'6"
81%Moderate
John Doe — Sells, Arizona
UP11385 • Found May 28, 2013
View case
Sex ✓Male
Age 100%Est. 16–20 vs 17
Race 100%Hispanic
Location 92%39 mi away, same county
TimingFound 10 months after last seen
Height 100%5'6" vs 5'4"–5'6"
80%Moderate
John Doe — Arivaca, Arizona - unidentified case UP104178
John Doe — Arivaca, Arizona
UP104178 • Found Mar 3, 2023
View case
Sex ✓Male
Age 100%Est. 19–22 vs 17 when missing
Race 100%Hispanic
Location 100%4 mi away, same county
TimingFound 11 years after last seen
Height 100%5'2"–5'6" vs 5'4"–5'6"
80%Moderate
John Doe — Sells, Arizona - unidentified case UP92525
John Doe — Sells, Arizona
UP92525 • Found May 31, 2022
View case
Sex ✓Male
Age 100%Est. 25–40 vs 17 when missing
Race 100%Hispanic
Location 92%39 mi away, same county
TimingFound 10 years after last seen
Height 100%5'1"–5'5" vs 5'4"–5'6"
Hair 100%Black vs Black

These comparisons are generated automatically from public NamUs case data and are not confirmed identifications. Only DNA, dental or fingerprint comparison by investigators can confirm an identity. If you believe two cases are connected, contact the agency handling the unidentified case.

Unidentified photos are blurred because many are post-mortem. Tap a photo to reveal it.