Investigators are searching for the four male suspects and are watching the surveillance footage for clues - Representational Image iStock

A 91-year-old Brooklyn man died in front of his 100-year-old wife after a group of robbers broke into their home and tied them up on Wednesday (11 October), police said. The incident has also left the elderly woman injured.

The couple, identified as Waldiman and Ethlin Thompson, were inside their Bedford-Stuyvesant brownstone when four men broke into the three-story home at around 3:30pm local time (8:30pm BST) and started attacking them, police said.

The men threw a blanket over Ethlin Thompson's head first and did the same with her husband and then tied the pair up, New York Daily News reported.

The robbers rummaged through the apartment and police are not sure if they have taken anything with them.

Authorities said they responded to the incident after they received a 911 call from Ethlin Thompson who had managed to free herself.

Waldiman who was unable to free himself was found unresponsive inside their home. He was rushed to Interfaith Hospital, where he was pronounced dead. Ethline is being treated for minor rope burns.

Investigators believe that the man may have died of shock, because he had no other injuries, according to ABC's New York station WABC.

The official cause of his death has not been determined.

Neighbour Paul Paterson, 55, who was outside at the time of the incident, told The New York Post that he saw the lady moments after the attack.

"I came walking up the block from work and she came running out the house screaming," Paterson said.

"This was the first time I ever saw her screaming. She said, 'They robbed me and my husband and tied us up, they came in from the back. My husband laying there and might be dead.' I said I can't go in there because it would be a crime scene."

Investigators are hunting the four male suspects and are watching the surveillance footage for clues. "We're treating this as a homicide home invasion robbery," NYPD Deputy Chief Michael Kemper, the commanding officer of Brooklyn North said.

Family members think the robbers were looking for cash since Ethlin Thompson would often give out money to people in need, NY Daily News website reported.

The police have reportedly taken a man into custody for questioning although it is not clear if the man will be charged.