NEW YORK — A Broadway vocal coach who suffered massive head trauma after an attacker shoved her to the ground outside her Manhattan apartment last week has died, the NYPD said. 

Barbara Maier Gustern succumbed to her injuries on Tuesday, NYPD Chief of Detectives James Essig said at a news briefing, calling the assault that led to her death an "unprovoked, senseless attack."

"We’re asking the public’s help in solving this disgusting and disgraceful offense committed against a vulnerable, elderly female who was doing nothing but walking down the streets of New York City," Essig said. 

Before Gustern's death, her friend, Barbara Bleier, told NY1 she and a few other people were rehearsing for a cabaret show Gustern was directing on March 10, the night she was attacked.

They left Gustern's apartment, located near West 28th Street and 8th Avenue in Chelsea, and went their separate ways. Bleier was waiting for a cab in the lobby of the building when a man came pounding on the front door.

“A young man, a good Samaritan, was bringing Barbara in, and she was covered in blood," Bleier recalled. "He was holding her up and we were, of course, totally stunned. She said, ‘I’ve never been hit so hard in my life.’”

Essig on Tuesday said Gustern was walking outside the building when a female suspect wearing a black jacket crossed the street and pushed her from behind. The attack forced Gustern to hit her head, police said.

“It's probably one of the more horrible things that I've ever experienced,” Bleier said. “She was singing and really singing beautifully, and within 10 minutes, she was covered in blood.” 

Bleier, who helped rush Gustern to the hospital, said her friend started to lose consciousness in the ambulance. She was taken to the hospital for a CT scan, where they discovered massive bleeding in her head. She was then rushed to Bellevue Hospital's trauma center. 

After the attack, Gustern was "unresponsive," Bleier said, adding that there was "still damage to the left side of her brain, which means paralysis to the right side and difficulty verbalizing."

Gustern was a well-known vocal coach for those on Broadway, and most notably for Debbie Harry, lead vocalist for “Blondie.” 

“She has been a huge influence on me, and I attribute some of my success, or a lot of my success, to her as a vocal coach, and her generosity as a human being, and her great sense of humor,” Harry told NY1.

In a statement released following Gustern's death, Harry said she was "going to miss having Barbara around."

"I will be using her warm up exercises on my next tour and into the future tours," Harry said. "She has been a wonderful inspiration to all her students. This is indeed a sad day in NYC."

Those closest to Gustern said she was one-of-a-kind. 

“She’s 87 years old, she weighs about 85 pounds and she’s like a teenager,” longtime friend Penny Arcade said. “She represented for so many people what was possible for life in your 80s. She's been robbed of her vitality, and we've been robbed of her vitality, her wisdom, her support, her love for her community.”

“She is such an extraordinary woman,” Bleier added. “In fact, when the EMS were there, they said, ‘What medicine do you take?’ and she said, ‘None.’ What 87 year old do you know that takes no medicine?”

“She's just one of those human beings who's always there when you need her to be there,” Bleier added.

Anyone with information about the incident is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS.