Police identified the suspect as 23-year-old Christian Falero. They charged him with second-degree murder and robbery.
Police say Falero was arrested Tuesday after he knocked on several doors of his apartment building in the Washington Heights section of Manhattan and then stabbed the people who answered. Police say a knife was recovered.
Police say 81-year-old Ignacio Reyes-Collazo was killed. Police say three women, ages 60 to 85, were stabbed and a 22-year-old woman was punched.
They were all taken to area hospitals; one was in critical condition while the other three were stable.