A man previously convicted of killing dogs in Colorado has been arrested in Arizona on a murder charge.
Matthew Dieringer, 35, is accused of murdering Frank Quaranta, 67, at his Scottsdale home in “a targeted attack,” according to a press release from the Scottsdale Police Department.
At a hearing on Sunday, September 8, a Maricopa County prosecutor claimed Dieringer “beat the victim to death.”
“This was a very violent and horrific murder,” the prosecutor stated during 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 stated that Dieringer was on probation at the time of the slaying and had prior felony convictions for animal cruelty.
According to Denver7, Dieringer was arrested at a Days Inn in Centennial, Colorado, on July 26, 2020, for killing two of his roommate’s dogs and dismembering one. He was sentenced to 18 months in prison following the 2023 conviction, according to Denver7.
The Maricopa prosecutor described Dieringer as “an extremely dangerous individual.”
Police were called to Quaranta’s Scottsdale home around 1:30 p.m. on Sept. 1, 2025, after he failed to show up for work or answer his phone, according to a probable cause statement obtained by PEOPLE. Officers forced their way inside the house and discovered 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,” according to the statement.
Investigators discovered “bloody handprints and what appeared to be bloody sock-covered foot impressions near the victim’s body” as well as “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 claimed Quaranta had “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,” according to 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 charged with first-degree murder, told the judge, “You are being given incorrect information about me, including my name.”
Dieringer was on probation for theft in Arizona when he was killed on June 20, 2024, after attempting to assault a man walking down the street and steal his sunglasses. He pleaded guilty to theft and misdemeanour assault.
The same day, he allegedly approached a woman walking her dog in downtown Phoenix and asked if he could pet it. “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,” according to the declaration of probable cause.
Shortly thereafter, he allegedly kicked another woman’s dog, “causing the dog to fly out of its leash and into the roadway,” according to the statement.
Quaranta worked at the Wesley United Methodist Church’s schooling center, according to church leaders.
“Frank was a tireless advocate for the unhoused, and his kindness and compassion touched everyone he served,” a pastor told AZfamily.
