NBC Dateline: How was Denise Hallowell murdered?

Denise Hallowell, a former teacher, was found murdered with an ax still embedded in her head inside the lakefront home in Florida in July 2019. The discovery was made by her adoptive son, Carlos Hallowell, 17, who then called 911 and told them that he slept through the incident. There were no visible signs of a break-in at the house.

Eventually, digital evidence was used to implicate Denise's adoptive son Carlos in the crime. The teenager later admitted to attacking the 57-year-old victim with the murder weapon in a fit of rage over because he was angered by a recent dispute over his schooling but claimed to have blacked out while attacking her. He was found guilty of premeditated murder two years later.

An all-new NBC Dateline Friday mystery is slated to revisit Denise Hallowell's horrific slaying on August 18, 2023. The episode titled Horror at the Lake will air on the channel at 9:00 pm ET.

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Denise Hallowell was found with an ax embedded in the back of her head in July 2019 at her lakefront house

According to Fox 13, Denise Hallowell had adopted two sons and first made headlines in September 2015 when she was arrested and accused of abusing the younger, 12-year-old son, who was adopted from Honduras. The allegations stated that the school teacher physically abused him by locking the boy inside a room and starving him.

Due to a lack of evidence to back up those claims, Denise was released. Her second son Carlos, who was 14 years old at the time, defended her. Back then, she had told investigators that her younger son had been troubled for years. This information was corroborated by Carlos. However, she lost her job and reputation in the community as well as one of her sons.

The second appalling event came in the summer of 2019 when Carlos Hallowell, then 17, made a distressing 911 call on the evening of July 13 and told the operator that his mother, Denise Hallowell, was dying. First responders arrived at their lakefront Florida home to find the 57-year-old dead of severe ax wounds and the weapon still embedded in the back of her head.

According to The Cinemaholic, Carlos told officers that he slept through the incident and was only awakened from his nap by the dogs' loud barking. He then discovered Denise brutally murdered in her bedroom. But there were no visible signs of a forced entry at the crime scene, and immediately, all suspicion fell on the son, who maintained his innocence in the matter.

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Denise Hallowell's adoptive son Carlos was linked to her ax murder using digital evidence found in the lake

During the investigation, detectives found the victim's iPhone and three security cameras, which had been removed from the house, at the bottom of the lake, as per the Citrus County Chronicle. The digital data extracted from the devices refuted Carlos' claims about the happenings, especially the statement that he was napping while his mother was being mutilated by an ax.

The outlet reported that detectives used phone GPS and timetables of device activities to map out the teenager's movements from the time the murder was committed until the 911 call was made. Then, on September 16, the 17-year-old was once again brought in for questioning and confronted with the digital evidence when he admitted to throwing the devices in the lake because he "panicked."

Carlos eventually changed his story and admitted to having a history of bickering with Denise Hallowell. He told detectives that the two argued over his schooling that afternoon while driving home from a funeral in St. Petersburg. Denise was allegedly about stop paying for his schooling because he wished to pursue technical college instead of a four-year degree.

Other allegations made by the teenager included accusing his adoptive mother of being verbally abusive. Carlos Hallowell reported said,

"She [Denise] let me have it, big time ... telling me I’m a worthless piece of (expletive) because of what I want to do."

Carlos revealed that Denise was napping when he took out his ax from the shed and took it to the garage to sharpen it, but he only intended to chop wood. The teenager then walked up to her bedroom where she was sleeping but claimed to have blacked out and only woke up to find her sharp weapon embedded in her head.

Fox 13 reported that Carlos Hallowell was found guilty of premeditated murder in Denise Hallowell's slating on July 9, 2021. He was later sentenced to life in prison and will be eligible for a sentence review only after 25 years.

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Learn more about Denise Hallowell's ax murder case on NBC Dateline's upcoming episode this Friday.