John L. Keenan, the New York Police Department’s chief of detectives who oversaw the manhunt leading to the August 1977 arrest of David Berkowitz, the “Son of Sam” serial killer, died on Thursday in Mineola, N.Y., on Long Island. He was 99.

His death, at NYU Winthrop Hospital, resulted from congestive heart failure, his grandson Kevin Brennan said.

Mr. Berkowitz had terrified the city in a yearlong string of nighttime shootings. Chief Keenan obtained his confession hours after he was captured without a struggle outside his apartment building in Yonkers.

As he told it, Mr. Berkowitz said, “I know you. You’re detective — Chief Keenan.”

“And I said, ‘Yeah? Who are you?’