Ms. Trott was born and raised in New York City, he said, and she was passionate about animals. She started her own rescue organization several years ago, he said.

“She did everything for dogs, pets, birds,” Mr. Boscia said. “She would never hurt anyone.”

Helen Stein, who lives on the 16th floor, also recalled Ms. Trott as a lover of dogs and one of the residents who helped with gardening at the building.

“I wouldn’t say she was an easy person, but I was totally unaware that she had any enemies or anything like that,” Ms. Stein, 72, said. “I just didn’t really know her well.”

Another neighbor said Ms. Trott lived alone.

“It’s totally shocking to me because I never felt safer anywhere in my whole life than this place,” Ms. Stein said.

Martha Wetterhall Thomas was a colleague of Ms. Trott’s about four decades ago when they both worked for BBDO, an international advertising agency with its headquarters in New York City.

“She was fun and a little crazy, and she was very smart and great at what she did,” Ms. Thomas, who lives in South Carolina, said in a phone interview. “She was somebody I looked up to.”

Ms. Thomas said she hadn’t talked to Ms. Trott in about 25 years, but she recalled an afternoon when a man stole Ms. Thomas’s purse as the two friends were leaving a bank in the garment district during their lunch hour. Ms. Trott chased the thief down Sixth Avenue and managed to pin him down to the ground with help from garment workers in the area.