When a parking ticket, issued to a car seen parked near the scene of one slaying, finally led detectives on Aug. 10, 1977, to the Yonkers home of Berkowitz, a 24-year-old postal worker, Mr. Keenan was there to confront him. It was a climactic scene Keenan later recounted many times for journalists.
“I know you. You’re detective — Chief Keenan,” said Berkowitz, who had publicly taunted the police with notes during the hunt.
“Who are you?” Mr. Keenan asked.
“I am the Son of Sam,” Berkowitz replied.
Mr. Keenan’s work on the case came near the end of a 37-year career with the department. He announced his retirement five months later when a new commissioner took office and wanted to appoint his own top deputies.
Notable deaths in 2019: Elijah Cummings, Cokie Roberts, Toni Morrison and others we have lost this year
During World War II, Mr. Keenan was a lieutenant in the Army’s Counter Intelligence Corps. He landed on Utah Beach in the D-Day invasion and participated in the Battle of the Bulge and the liberation of Paris. Author J.D. Salinger, who was writing “Catcher in the Rye” between battles, was in Mr. Keenan’s infantry division and became a lifelong friend.
After leaving the NYPD, Mr. Keenan became vice president of operations at the New York Racing Association, which operates the Belmont Park, Aqueduct and Saratoga thoroughbred horse tracks.
He lived in Rockville Centre on Long Island. He and his wife, Sara, were married for 73 years. Two of their three daughters preceded him in death.
Mr. Keenan’s leadership of the Son of Sam manhunt cemented his reputation as a tough but tactical police officer.
Searching for the killer, he oversaw a task force dubbed Operation Omega that by one count involved 75 detectives and more than 200 uniformed officers. He also used televised news conferences to talk directly to the killer, trying to coax him into stopping his crime rampage and surrender.
“Son of Sam, we now know you are not a woman hater — and know how you have suffered,” Mr. Keenan said at a news conference after the killer identified himself by that nickname in a note left at the scene of a double homicide in April 1977. “We wish to help you, and it is not too late. Please let us help you.”
Recounting the manhunt to TV news station NY1 for the 40th anniversary of the arrest, Mr. Keenan said even he had been afraid of where the gunman might strike next.
“My daughter Joan was a teenager, and I had two other daughters,” Keenan said. “And I was worried about them. I realized most fathers were in the same position: They were worried about their daughters. It became kind of a panic in the city.”
The killer had been taunting investigators in letters to New York Daily News columnist Jimmy Breslin. In one, he offered detectives words of encouragement.
“Please inform all the detectives working the case that I wish them the best of luck,” Berkowitz wrote. “Keep Em digging, drive on, think positive, get off your butts, knock on coffins, etc.
“Upon my capture I promise to buy all the guys working on the case a new pair of shoes if I can get up the money.”
Read more Washington Post obituaries