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New details emerge in death of woman allegedly drowned by her son at Long Island home

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COLD SPRING HARBOR, N.Y. -- It's a crime that has shocked a quiet, affluent Long Island community.

Residents in Cold Spring Harbor are reeling from the murder of a woman, at the hands of her own son.

Denis Cullen, 23, was charged with second-degree murder in connection with the death of his mother. (Cold Spring Harbor Police)

Denis Cullen, 23, was charged with second-degree murder in connection with the death of his mother. (Cold Spring Harbor Police)

Police say they have 23-year-old Denis Cullen's confession on videotape after an interrogation where he says he intentionally drowned his mother in the backyard pool after an argument escalated at the family's White Hill Road home in the village of Lloyd Harbor.

Thursday morning, Cullen went before a judge at First District Court in Central Islip. Cullen was arraigned on a charge of second-degree murder.

Suffolk County police say Cullen confessed to murdering his mother with his bare hands.

At his arraignment, the prosecutor laid out gruesome details.

Cullen and his mother 63-year-old Elizabeth Winn Cullen had been arguing about him taking his medication.

Things escalated and Cullen allegedly put her in a headlock and dragged her to the deep end of the pool. A violent struggle ensued and she drowned.

Cops say he took her body out of the pool and laid her beside the shed. He then went back to the house, showered and took money from his mother's purse. Cullen hopped on the LIRR into Manhattan to see his sister in the city. There, he told her what he allegedly had done. She called their father who called 911.

Police responded and made the horrific discovery. Cullen later returned home while authorities were still there.

"While we were processing the scene the suspect returned to the home and we placed him under arrest," said Timothy Sini, Suffolk County Police Commissioner.

Prosecutors say Cullen does not have a prior record. They're looking into his possible history of mental illness.

An engagement announcement in New York Times from 1983 show Elizabeth Cullen goes by the name Winn. She and Cullen's father have been married for 33 years. Her own family has prominent military ties. Her father was Vietnam War hero Maj. Gen. George William Casey. Her brother is former Army Chief of Staff George Casey.

She owns an interior design company, Winn Cullen Interiors, in town. The murder has hit this quaint community hard.

Denis Cullen pleaded not guilty to a charge of second-degree murder.

Bail was set at $5 million cash or $8 million bond.

If convicted he's looking at 25 years to life in prison.