ALBANY, N.Y. -- The "Son of Sam" serial killer who terrorized New York City 40 years ago is in the hospital. New York state prison officials said Tuesday that 64-year-old David Berkowitz was transferred to a hospital from the upstate maximum-security prison where he is serving a life sentence.

Officials would not comment on why he was in the hospital, but the New York Post and the Times-Union of Albany reported that he was transferred to undergo heart surgery.

Berkowitz, who called himself "Son of Sam," set the city on edge with late-night shootings that killed six people and wounded seven. He primarily targeted young women sitting in cars before his arrest on Aug. 10, 1977.

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Berkowitz now says he is a born-again Christian and is "very sorry for what happened."

Last August, in his first major TV interview in a decade, Berkowitz told CBS News correspondent Maurice DuBois, "I was just very lost and confused. There was a battle going on inside me."

He described the killing spree as "a break from reality" and said, "I thought I was doing something to appease the devil. I'm sorry for it."