Scottsdale police arrested Matthew Dieringer, 35, and charged him with murder after investigators found the body of his 67-year-old roommate, Frank Quaranta, inside a townhome following a welfare check on Sept. 1.
Officers forced entry to the residence after being unable to make contact with Quaranta and discovered him deceased from apparent blunt-force trauma, police said. Detectives and crime‑scene specialists processed the home for several hours, and investigators said evidence at the scene pointed to Dieringer.
Scottsdale Police said Dieringer had been living with Quaranta after the two met at a church homeless outreach event. Authorities described Dieringer as having a history of homelessness and said he had been "described as manipulative and charismatic, often befriending others to assist him with a place to stay."
Police received a tip that Dieringer had been spotted in Phoenix and arrested him on a probation violation stemming from a 2024 theft case, Scottsdale Police Sgt. Allison Sempsis said. "That was what the initial arrest was for," Sempsis said. Officers served a search warrant for forensic evidence after Dieringer was taken into custody, and investigators said that evidence "tidied up any loose ends for the homicide."
Prosecutors told the court they had a presumptive DNA match to blood found at the crime scene. "The subject allegedly beat the victim to death. This was a very violent and horrific murder," Brooke Gaunt of the Maricopa County Attorney's Office said at Dieringer's first court appearance.
A judge ordered Dieringer to be held at the Maricopa County Jail on a $3 million bond. Dieringer told the judge, "I believe that you are being given wrong information entirely about me and my name," and later referred to the proceeding as "illegal" before concluding the hearing with a brief comment invoking religion.
Records and news reports show Dieringer has a prior criminal history, including a 2020 conviction in Colorado for killing and dismembering two dogs belonging to a former roommate. When the dogs' owner requested a welfare check at the mobile home they shared, deputies reported finding walls covered in blood. Teller County animal control described the scene as "difficult." Dieringer was sentenced to 18 months and received credit for 705 days served; he subsequently relocated to Arizona, according to court records and local reporting.
Scottsdale police said detectives continue to investigate the case and are coordinating with the Maricopa County Attorney's Office. No further criminal charges beyond the homicide count were announced at the initial hearing.
The arrest follows an alertness to community tips and the use of forensic evidence to link a suspect to the scene, authorities said. The case remains under investigation as prosecutors prepare to move forward with charging decisions and possible further proceedings.