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Woman who encountered 'charismatic' murder suspect questions county attorney's office
A woman who encountered the accused Scottsdale murder suspect, Matthew Dieringer, in summer 2024 is questioning the county attorney's office for never prosecuting him for allegedly slamming her dog into concrete.
PHOENIX - A Phoenix area woman is questioning why the Maricopa County Attorney's Office never prosecuted the suspect who allegedly slammed her dog into the concrete last summer.
That suspect, as it turns out, was Matthew Dierenger, the same person who, according to investigators, is accused of murdering a 67-year-old Scottsdale man.
Matthew Dieringer: 'charismatic' murder suspect refused to give DNA sample despite search warrant, police say
Newly-obtained court documents are giving us a better picture of a murder suspect who Scottsdale Police say was described as "manipulative and charismatic."
Big picture view:
Matthew Dieringer has been described by Scottsdale Police officials as "charismatic" and "manipulative." That's a description Kim Shedd agrees with.
Shedd talked about how Dieringer approached her dog last summer, and the trauma that unfolded.
"I saw him, we locked eyes, and we fell in love," said Shedd, describing the moment she met her dog Mateo.
Mateo was rescued from a shelter, and became Shedd’s loyal companion for nearly 15 years. In June 2024, however, Shedd said Mateo’s physical and mental health took a major blow, after coming face to face with Dieringer.
"There was no signs that told me that he would have done what he did," said Shedd.
Dig deeper:
According to court records, Shedd was walking Mateo near 1st Avenue and Van Buren Street in Downtown Phoenix when Dieringer approached them.
"He tells me how much of a cute dog, and he wanted to really pet him," said Shedd. "Mateo's usually friendly, outgoing, and I said ‘sure, you can pet Mateo.’ He reaches down and grabs Mateo and picks him up."
Kim didn’t expect what happened next.
"He throws his arms back, and he throw Mateo down to the ground," Shedd recounted. "He [threw] him down so hard [that he threw] him out of his harness."
At the time, Mateo didn’t have visible injuries, but was in pain. Within 10 minutes, Phoenix Police say Dieringer kicked someone else’s dog off its leash, and then allegedly tried to punch a man before stealing his glasses.
In all, there were three separate attacks over the span of 40 minutes.
Timeline:
Months later, police arrested Dieringer on charges of domestic animal cruelty - mistreatment and robbery. Ultimately, Dieringer would only be indicted on one count of theft and one count of assault.
Shedd has learned that charges were never filed for either of the alleged assaults on the dogs.
"Gut punched and sickened and saddened," said Shedd.
By April 2025, Dieringer plead guilty to theft. He was sentenced to supervised probation, agreed to get mental health screenings, and report to his probation officer.
Ultimately, it took a month for Dieringer to violate the terms by not checking in with his probation officer. It meant a punishment of a 12-month stint in prison, but officers couldn’t locate him.
Per court documents, Dieringer is homeless, and the listed address of his residence is a south Phoenix church where he met Frank Quaranta.
Investigators say Quaranta, who worked at a heat relief center at the church, let Dieringer live with him in Scottsdale.
By early September, the 67-year-old was found beaten to death in his home. Scottsdale Police quickly identified Dieringer as the suspect in Quaranta’s murder, arresting him days later. Dieringer has plead not guilty to murder, and remains in Maricopa County Jail on a $2 million bond.
Court records reveal Dieringer’s history of animal cruelty, stemming from a 2020 Colorado case in which he mutilated and killed his roommate’s two dogs. For that case, Dieringer pled guilty, and was sentenced to 18 months in prison in 2023.
MCAO explains decision not to file charges in Shedd's case
As for what happened to Mateo in 2024, we asked the Maricopa County Attorney’s Office why Dieringer wasn’t charged with animal cruelty.
What they're saying:
In their response, officials with MCAO said there was no reasonable likelihood of conviction for the animal cruelty, due to no proof of injury. A statement reads, in part:
"Current statutes do not provide prosecutors with the recourse to file felony charges in instances where a pet has been assaulted or abused but was not tortured, seriously physically injured, or killed. No information or veterinarian records were submitted with the case to indicate either dog was physically hurt, and there was no information provided in the police report to prove physical injury."
Officials with MCAO also said Phoenix Police’s report had no information or vet records to show physical injury. MCAO ultimately recommended for misdemeanor charges of disorderly conduct to be sent to prosecutors.
The other side:
Shedd showed us Mateo’s medical records that she said were sent to Phoenix Police. She spent nearly $1,000 for an emergency visit, and Mateo was treated for a "traumatic injury," and given medication for "back pain."
Shedd said Mateo was never the same, refusing to go outside, and his personality was no longer friendly. Mateo's health ultimately declined, and Shedd put him down a few months after the incident allegedly involving Dieringer.
"It was so hard because I couldn't understand," said Shedd. "It was hard because knowing someone else was the reason why I couldn't enjoy this last moment, but it was because of someone else."
We have reached out to the Maricopa County Adult Probation Department, asking what else could have been done when Dieringer violated his probation and not arrested until months later. A spokesperson says probation supervision histories are designated as closed, due to an Arizona Supreme Court law.