The most recent incident happened on East 106th Street and 3rd Avenue in East Harlem around 7:30 p.m. on October 5.
The suspect was caught on surveillance video talking on a cell phone near the scene, where police say he followed a 45-year-old man into his apartment building, threatened him with a knife and removed $230 from the victim's wallet.
In each incident, the suspect follows the victim into the building vestibule, where he brandishes the knife and demands property. There were no reported injuries these incidents.
The other two incidents happened on October 1 in the vicinity of East 109th Street and 1st Avenue and on October 2 at East 102nd Street and 1st Avenue. The victims, a 25-year-old man and a 24-year-old man, had cash and cell phones stolen.
The suspect is described as a Hispanic male in his mid 20s. Police also released a photo of a black van that may be the suspect's getaway vehicle.
Anyone with information in regard to these incidents is asked to call Crime Stoppers at 1-800-577-TIPS (8477).