'She sees blood everywhere': Teen girl comes home to find 4-year-old brother dead after mother suffocated him with plastic bag, cops say

Insets, left to right: Finley Cullom (Diana Cullom/Facebook) and Diana Cullom (Pinellas County Jail). Background: The home in St. Petersburg, Florida, where Cullom allegedly killed her son Finley (WFLA/YouTube).

A teenage girl arrived home from school Tuesday afternoon to a horrific scene: Her 4-year-old brother dead in their bloodied mother's arms on a bed, Florida cops say.

The St. Petersburg Police Department said 43-year-old Diana Elizabeth Cullom suffocated Finley Cullom with a plastic bag. The mother of four is charged with first-degree murder.

"She walked into the house, she sees blood everywhere, she sees her 4-year-old brother … you come to the conclusion," Chief Anthony Holloway told reporters.

Cops responded around 3:30 p.m. Tuesday to a home in the 1700 block of Tanglewood Drive NE for a report of a person bleeding. They went inside to find the boy dead and his mother suffering from apparent self-inflicted stab wounds. Paramedics took Cullom to the hospital with non-life-threatening injuries. She has since been released and is now in the Pinellas County Jail.

Because there was so much blood in the house, investigators initially believed Cullom stabbed her son to death. But further investigation revealed she allegedly suffocated Finley with a plastic bag. Cops also found a note reportedly written by Cullom in the home but they did not divulge what it said.

Cullom provided statement to authorities after receiving her Miranda rights, but that was redacted from the initial police report. Cops have not released a motive for the slaying or revealed what led to the killing.

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Cullom's husband, a local dentist, was not at home at the time, police say. Cullom helped her husband start Crescent Lake Family Dentistry, according to her biography. They had four children together.

"In her free time she loves to spend time with friends and family, including her seven siblings, time with God, construction, fishing, architectural design and renovation projects, gardening, business ventures, charity work, travel, reading/research, music festivals and almost any outdoor activity," the biography said.