Murder of Donal O’Sullivan by Daniel Tennity profiled on Buried in the Backyard

Oxygen is re-airing the Buried in the Backyard investigation into the murder of Donal “Dee” O’Sullivan, who was choked to death by Daniel Tennity at the victim’s home in Melbourne, Florida.

The 42-year-old O’Sullivan was a successful tech entrepreneur who decided to take early retirement. He moved from Georgia to Florida, where he struck up a seemingly unlikely friendship with a group of skateboarders.

Unfortunately, he suddenly disappeared in late September 1998. His brother reported him missing after failing to hear from him for some time.

Brevard County deputies performed a welfare check and could find no sign of O’Sullivan. Rather worryingly, they did find a mattress that was covering a large amount of blood.

The cops also learned that someone called Eric Marshall had been attempting to cash checks from O’Sullivan’s account. And someone had also been accessing his mail.

Marshall was soon identified as Daniel Tennity, a 26-year-old skateboarder from New York. Tennity was living with his friend at a property rented under O’Suillivan’s name. Tennity already had a conviction for burglary in NY and was in violation of his parole for leaving the state.

The cops soon learned Tennity had taken $28,575 from O’Sullivan’s account. He claimed to be employed by his victim to run errands, but the cops weren’t buying his story.

Evidence mounted against Daniel Tennity in Donal O’Sullivan killing

A search of Tennity’s rental home uncovered a forged deed in the killer’s name for an empty plot in Canaveral Groves, a rural area north of Melbourne. They also found a rental agreement for a backhoe.

On the plot, investigators found an area of disturbed ground that contained a meat freezer with the decomposing remains of O’Sullivan. The coroner had to use dental records to make the identification.

The cops concluded that O’Sullivan discovered his killer was stealing from him, and the pair got into a violent confrontation. Tennity then strangled his victim before leaving the remains on the mattress for a few days.

Tennity then purchased the meat freezer, but for unknown reasons, he never preserved O’Sullivan’s remains by plugging in the appliance; he simply used the freezer as a coffin.

Daniel Tennity bragged to fellow inmates about Donal O’Sullivan murder

While in custody, Tennity asked a friend to send his Bible to his mother; when the friend opened the Bible, they found O’Sullivan’s credit cards and other documents stashed inside. The killer also bragged to other inmates about committing murder.

Tennity pleaded guilty to second-degree murder and multiple other charges, including grand theft and forgery. He was sentenced to 40 years.

This episode of Buried in the Backyard re-airs Friday at 8/7c on Oxygen.