UPPER WEST SIDE, Manhattan (PIX11) — A 74-year-old woman was found dead with her hands and feet tied inside her Upper West Side apartment, authorities said Friday.

Maria Hernandez was found by her sister lying unresponsive on the floor, bound with rope, and covered with a sheet around 9:55 p.m. on Wednesday inside the apartment on West 83rd Street near Columbus Avenue, police sources told PIX11 News. 

Hernandez was bound and gagged with fractures and bruises on her body, authorities said. First responders pronounced her dead at the scene.

“We are all in shock. The question is – why would someone want to do that to our mother?” said Lucia Hernandez.

Police sources told PIX11 that Hernandez and her sister, who live in the same building but in different apartments, had gone to a show earlier in the evening and returned home around 6 p.m. A neighbor celebrating a birthday stopped by Hernandez’s apartment with a piece of cake around 6:30 p.m., sources said. That was apparently the last time Hernandez was seen alive.

Around 8 p.m., Hernandez’s daughter tried to get in touch with her but no one answered, according to sources. The daughter called her aunt and asked her to check on Hernandez, leading to the discovery of her body.

“She was very friendly toward everybody here. She was always introducing us to her friends,” said another daughter, Carmen Taveras.

Detectives took inventory of the ransacked apartment to determine whether Hernandez, who lived alone, was robbed, police sources said, adding that there were no signs of forced entry.

Police believe it may have started out as a robbery that took a deadly turn and that the same person responsible broke into the superintendent’s office in the basement of the building and stole the building’s security system. Investigators looking for surveillance video found the DVD missing and cables cut, sources said.

No arrest had been made as of Friday evening. Sources told PIX11 News detectives are now looking for a former building worker for questioning.

Maria Terrero, Hernandez’s sister, said she doesn’t know who would want to harm her sister.

“She was an excellent human being, kind, loving, wonderful,” Terrero said.

Submit tips to police by calling Crime Stoppers at 1-800-577-TIPS (8477), visiting crimestoppers.nypdonline.org, downloading the NYPD Crime Stoppers mobile app, or texting 274637 (CRIMES) then entering TIP577. Spanish-speaking callers are asked to dial 1-888-57-PISTA (74782).