A 16-year-old girl arrived home from school Tuesday afternoon and found her 4-year-old brother dead and their mother injured inside a St. Petersburg house, police said. By Wednesday, detectives had arrested the mother, 43-year-old Diana Elizabeth Cullom, on a first-degree murder charge in the boy’s death.
St. Petersburg police said the discovery was made shortly after 3:30 p.m. Tue., Jan. 27, at a home on Tanglewood Drive NE. Officers at first believed the child had been stabbed based on blood throughout the residence and the mother’s injuries. An autopsy completed overnight found no stab wounds on the child and concluded he died by suffocation, authorities said. Investigators say Cullom sustained what appeared to be self-inflicted cuts and was treated at a hospital before being released to police custody. The case remains active as detectives review evidence collected from the home, including a handwritten note recovered by the teen, and await additional lab testing.
Police said the teenager found her mother holding her brother in a bed when she walked into the house. She called for help as officers and paramedics rushed to the scene. The boy, identified by relatives as Finley Joseph Cullom, was pronounced dead at the home. Detectives documented blood in multiple rooms, photographed the bedroom and hallways, and began canvassing the block for doorbell and security video that might show activity around the house before the teen arrived. “This is a heartbreaking case for everyone involved,” a police spokesperson said, noting that crisis counselors were made available to the teen and responding officers.
Detectives said initial statements and physical evidence pointed to Cullom as the lone suspect. She was taken to a hospital with cuts on her body and later interviewed by investigators. Police have not released a possible motive. The medical examiner’s preliminary findings listed suffocation as the cause of death; officials did not immediately specify whether an object or bedding was involved. Investigators said a note found in the home is believed to have been written by the mother, but its contents were not made public. No other children were reported inside the residence at the time of the discovery, and police said there were no prior calls for service at the address in recent months.
The home sits on a residential street in northeast St. Petersburg, a neighborhood of single-story houses and cul-de-sacs where after-school traffic is common. Neighbors described squad cars lining the block as crime-scene tape went up near dusk. Technicians placed evidence markers in the bedroom, collected clothing and linens, and sealed items in paper bags for transport. Patrol officers knocked on doors seeking footage from the afternoon, and detectives conferred with medical examiner staff about time-of-death estimates while the scene remained secured into the evening.
Authorities stressed that early references to a stabbing reflected what officers encountered on arrival but were superseded by medical findings after the examination. Police said they would update the case record to reflect the suffocation ruling and any additional evidence identified through lab analysis. Officials did not discuss the mother’s medical history or whether any prior welfare checks had been requested at the home. The department said it would review its response protocols in critical incidents involving juveniles, a standard step after child deaths investigated as homicides.
Cullom was booked on a count of first-degree murder. A first appearance in Pinellas County court is expected after processing, when a judge will consider pretrial detention and appoint counsel if needed. Prosecutors will review the investigative file and the medical examiner’s report to determine formal charges. Police said the teen who found her brother is with relatives as victim advocates coordinate services. Additional test results, including toxicology, could take several weeks, and officials said the timeline will be refined as digital evidence and interviews are analyzed.
Neighbors left small bouquets near the mailbox Wednesday morning as investigators finished grid searches inside the house. A nearby resident said officers asked about doorbell-camera alerts and daytime visitors. The block was quiet by midday, with a single patrol car returning to monitor the area. “It’s just devastating,” one neighbor said, recalling the steady stream of emergency vehicles the night before.
As of Wed., Jan. 28, police said Cullom remained in custody and the investigation was ongoing. Officials said they would release further details after the court appearance and once additional lab results are available.
Author note: Last updated January 28, 2026.