Investigators suspect Cullen had been intentionally drowned, police said. Denis Cullen then went into the home where he lived with his mother, father and one of his three sisters, and took a shower, Biancavilla said.
Denis Cullen Jr was arrested on Wednesday after detectives found the body of 63-year-old Elizabeth Cullen in the backyard of their Cold Spring Harbour home in Long Island. He then allegedly dragged his mother into the pool and put her in a headlock. A violent struggle ensued and she drowned.
He waited until she stopped moving and carried her body out of the pool and placed it next to a shed and covered her body with a dinghy, Biancavilla said.
It is unclear who called police.
Lloyd Harbor police contacted Suffolk police at about 4 p.m., and officers from the Suffolk police department's Second Precinct, Emergency Service Unit and the Homicide Squad responded, police said.
When Cullen returned to the home, he was arrested without incident, WCBS 880's Marla Diamond reported.
Cullen has a history of drug addiction and mental problems. Elizabeth Cullen ran Winn Collen Interiors out of Cold Spring Harbor.
Sini said Cullen jnr returned to the scene of the crime and cops cuffed him. Gen. George William Casey, who was killed in a 1970 helicopter crash in Vietnam.
If convicted he's looking at 25 years to life in prison.