By admin 
SCOTTSDALE, AZ (AZFamily) — A man accused of killing a Scottsdale resident he befriended has been found incompetent to stand trial, putting the case on hold while he receives treatment.
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Matthew Dieringer has been in custody since September 2026, when he was arrested in connection with the death of Frank Quaranta. Police found Quaranta dead in his home near 68th Street and McDowell Road after friends requested a welfare check. He had signs of blunt force trauma, and investigators described the killing as a targeted attack.
Investigators said Dieringer had been living with Quaranta for several months. The two reportedly met at a church cooling center where Quaranta worked.
Law enforcement described Dieringer as having a history of homelessness and known to be “manipulative” and “charismatic.” Scottsdale police said Quaranta’s goodwill may be why he was killed.
Court documents show an evidentiary hearing was held in late August to assess Dieringer’s competency. A third-party mental health expert noted that he displayed “disruptive and erratic behavior,” according to the documents.
The review also described Dieringer’s frustration that his attorney did not agree with his belief that his social media influence was relevant to the criminal case.
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Dieringer will be committed to the Maricopa County Correctional Health Services Restoration Program for treatment, according to the ruling. His next hearing is scheduled for Nov. 11.
Arizona’s Family previously spoke with a retired FBI agent and forensic psychologist, who both said said that Dieringer was likely a “dangerous, impulsive, thrill-seeking criminal known to use his charm to earn other’s trust.”
Leaders of the Wesley United Methodist Church in Phoenix said Quaranta was a beloved staff member who was a “tireless advocate for the unhoused, and his kindness and compassion touched everyone he served.”
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