COLD SPRING HARBOR, N.Y. (CBS NEWS)-- Police have arrested the son of a woman who they believe was intentionally drowned in a backyard pool outside her home in an affluent Long Island, New York neighborhood.

Suffolk County police say 23-year-old Denis Cullen faces a second-degree murder charge in the death of his mother, Elizabeth Cullen.

Police were called to their Cold Spring Harbor home Wednesday after receiving a request to check on the welfare of the 63-year-old woman, who was found dead in the backyard. Police say they believe she was intentionally drowned.

CBS New York reports the son lives with his mother and returned to the home while police were investigating the death. He was arrested less than two hours later.

Cullen is expected to be arraigned Thursday.

There’s no word on a possible motive.