He Once Dismembered 2 Dogs. Now He’s Accused of Killing a Beloved Advocate for the Unhoused By Christine Pelisek

A man who was convicted of killing dogs in Colorado has been arrested on a murder charge in Arizona.

Matthew Dieringer, 35, is accused of murdering 67-year-old Frank Quaranta, who authorities say was murdered at his Scottsdale home in “a targeted attack,” per a Scottsdale Police Department press release.

At a Sunday, Sept. 8, hearing, a Maricopa County prosecutor alleged Dieringer “beat the victim to death.”

“This was a very violent and horrific murder,” the prosecutor said at the hearing. “There was a strong weight of evidence against Mr. Dieringer, including presumptive DNA match to blood that was found at the scene.”

The prosecutor said Dieringer was on probation at the time of the slaying and had prior felony convictions that included animal cruelty.

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According to Denver7, Dieringer was arrested at a Days Inn in Centennial, Colo., on July 26, 2020 for killing two of his roommate’s dogs, dismembering one of them. He was sentenced to 18 months in prison after the 2023 conviction, per Denver7.

The Maricopa prosecutor described Dieringer as “an extremely dangerous individual.”

Police were called to Quaranta’s Scottsdale home about 1:30 p.m. on Sept. 1, 2025 when he didn’t show up to work or answer his phone, according to a probable cause statement obtained by PEOPLE. Officers forced entry inside the residence and found Quaranta dead at the top of the stairs with “extensive trauma to his head.”

“There was a metal sculpture lying on its side on top of the decedent’s head and an additional metal sculpture covered in blood on the floor nearby,” says the statement.

During a search of the home, investigators found “bloody handprints and what appeared to be bloody sock-covered foot impressions near the victim’s body” and “a bloody shirt and blood-soaked socks in a dirty clothes bin and blood on a larger pair of boots,” according to the statement.

Police interviewed coworkers, who alleged that Quaranta “allowed a subject to live with him for the past three months and was recently asking a coworker how to get the subject to move out of his house,” per the statement.

According to the press release, Dieringer has a “history of experiencing homelessness, and has been described as manipulative and charismatic, often befriending others to assist him with a place to stay.”

During the hearing on Sunday, Dieringer, who is facing a first-degree murder charge, told the judge, “You are being given wrong information about me entirely, and my name.”

At the time of the slaying, Dieringer was on probation for theft in Arizona after he attempted to assault a man walking down the street and stole his sunglasses on June 20, 2024. He pleaded guilty to theft and misdemeanor assault.

That same day, he allegedly approached a woman walking her dog in downtown Phoenix and asked her if he could pet her dog. “Matthew Dieringer then bent down and rather than petting the 14-year-old dog, [he] picked it up and then forcefully threw the dog to the ground,” states the probable cause statement.

Shortly after, he allegedly kicked another woman’s dog, “causing the dog to fly out of its leash and into the roadway,” per the statement.

Quaranta worked at the Wesley United Methodist Church’s schooling center, church leaders said, per AZfamily.

“Frank was a tireless advocate for the unhoused, and his kindness and compassion touched everyone he served,” a pastor said, according to AZfamily.