Residents were on edge in Stuyvesant Town in Manhattan on Sunday, following violent attacks on two elderly men there earlier this month.
Police released surveillance video of one of the incidents that happened Wednesday.
The suspect is seen attacking a 71-year old man in the building's lobby.
The older man's money was stolen and he suffered a broken arm.
Police say they believe the same suspect also grabbed a 77-year old man in a building entrance on November 3, attacked him and robbed him.
Some residents told NY1 the neighborhood needs better security, while others said it was a matter of vigilance.
"They have money to spend on ice skating rinks and things people don't need, but apparently they don't spend it on security," said a Stuyvesant Town resident.
"We need foot guards, the patrolmen around again," said another resident.
"The basic thing is you have to be careful and you have to watch what's happening around you," said a third.
"This is one of the safest places you could live in New York City," said a fourth resident. "I feel comfortable, in spite of the report of the robberies. I would think to be more aware of what is happening around you."
According to crime statistics, robberies have increased 5.6 percent in the neighborhood in the last year.
The suspect is described as in his 40s, about 5-feet-8-inches tall and 180 pounds.
Anyone with information on the attacks should contact the Crime Stoppers hotline at 1-800-577-TIPS, or text CRIMES and then enter TIP577, or visit www.nypdcrimestoppers.com.