NYPD Cold Case Squad looks at 1980 Manhattan murder of voice coach for Maya Angelou, Roberta Flack, Paul Robeson

What he found in a Manhattan apartment the morning of April 5, 1980, has stayed to this day with Carlos Gueits-Bonilla, a former opera singer.

His voice teacher and friend, Frederick Wilkerson — whose celebrity pupils included Roberta Flack, Maya Angelou and Paul Robeson — was dead in his Upper West Side bedroom, strangled and with several broken ribs.

“This has been grinding on me for almost 44 years, if you can imagine that,” Gueits-Bonilla said. “And I’ve never felt comfortable with nobody being arrested and charged with a crime.”

Gueits-Bonilla sent an email last year to former Manhattan District Attorney Cy Vance, whom he knew socially when he lived in Washington, D.C. That email helped bring new NYPD attention to the case.

NYPD Detective Robert Deckert, a member of the Cold Case Squad, hopes modern forensic analyses and a re-examination of fingerprints and other evidence will help crack the case.

“Cold cases are challenging,” said Deckert, who joined the force nearly 16 years ago and has been on the Cold Case Squad for two years. “There’s a lot of frustrations, a lot of walls.

“But you can’t give up.”

Gueits-Bonilla arrived at the apartment on W. 95th St. near Amsterdam Ave. late the night Wilkerson is believed to have been murdered.

“I always stayed with him when I was in New York,” said Gueits-Bonilla, now retired from a career as a respiratory therapist. “We’d go out to dinner. We’d BS. We were always dear friends.”

He wasn’t the only overnight guest — a woman who was another of Wilkerson’s students was also there. Gueits-Bonilla believes the killers had already left by the time he arrived.

When Wilkerson didn’t show up for breakfast the next morning, Gueits-Bonilla went into his bedroom.

He recalls finding Wilkerson, 67, lying with his head at the foot of the bed, a purple bruise the size of a finger near his right eye.

“I touched him — he was ice cold,” said Gueits-Bonilla, who turns 77 on Friday. “I took his pulse and of course there was no pulse.”

Gueits-Bonilla talked to the police that day. Students who showed up at Wilkerson’s apartment for private voice lessons left in tears when they heard their teacher was dead, he remembers.

After that, Gueits-Bonilla said, he never heard from police again.

Deckert said 24th Precinct police officers worked the case well.

”They did a good job,” he said. “It wasn’t a case that went cold for lack of trying.

“This was a tragic end for a guy that really had a wonderful life and career.”

The detectives determined that Wilkerson had two men to his place the night before he was found dead.

The three men went to Wilkerson’s bedroom for an encounter that went horribly wrong.

The killers were seen by the woman who was also visiting Wilkerson. She was not aware when the men left that Wilkerson had been murdered, Deckert said.

Deckert said the woman provided the description for police sketches of the suspects — two Black men believed to be in their 20s or 30s — but she did not know their names.

“The sketches are pretty good,” Deckert said. “I think someone knows these two men.”

Wilkerson, who was born in Texas, performed professionally in Europe under the stage name Gilbert Adams, according to the New York Public Library archives. In 1947, he was the vocal coach for the stage production of “Porgy and Bess.”

Angelou, who was a dancer in “Porgy and Bess” long before her fame as a poet, remembered nine years later Wilkerson stopping by her apartment in Hollywood with Billie Holiday.

Holiday later told Angelou: “You’re going to be famous—but it won’t be for singing.”

Wilkerson also published two articles considered standard references for music teachers and he founded a scholarship program for poor students in Washington, D.C. He also headed the Wilkerson Scholarship Choir, which appeared at the Kennedy Center, with Flack conducting.

Gueits-Bonilla sang opera until 1983, and then continued on with his respiratory therapy work.

Last year, while watching a television show involving cold cases and the NYPD, he decided to reach out to Vance, the former Manhattan DA.

Vance said he referred Gueits-Bonilla, who now lives near Washington, to a senior prosecutor still with the DA’s office. Eventually, Gueits-Bonilla connected with Deckert.

Gueits-Bonilla is thrilled that Deckert found the case file intact and that there is at least a chance at justice.

Wilkerson, he said, was charismatic, with a big voice and the mien of a football coach — direct and demanding, but always with an eye on getting the best out of them.

“He loved his students,” Gueits-Bonilla said. “He was very tough with them. like a football coach. He had a big, imposing voice and very clear. ‘I’m going to make it simple for you and if you can’t handle simplicity get the hell out.’

“I didn’t mind that at all.”

Wilkerson once told an interviewer: “You must think of your whole body as a sounding box.”

“You must feel every syllable you say all the way down to your feet, all the way to your toes,” he added.

“I tell my pupils to start practicing early in the day. You should start your voice early and keep it up all day, working while you talk. You’re singing all the time.”

Deckert asks anyone who knows anything about the suspects or the case to call Crime Stoppers at 1-800-577-TIPS.

“We never know what little piece will crack the case,” he said, “be it a small piece of information or be it a large piece of information.”