On Friday, the NYPD was canvassing Windsor Terrace, where another sex assault bumped the total to 20 in Brooklyn since March.
Martinez allegedly grabbed a woman from behind and groped her as she was walking near 36th Street and between Fourth and Fifth Avenues early Monday morning.
Police say Federico Chamorro Yax, 22, faces assault, sex abuse and forcible touching charges following two incidents.
Hernandez, 18, left the Special Victims Unit overnight moments after being charged in connection with the series of gropings.
An 18-year-old was apparently brought in from Queens on Monday night after a building superintendent on the Upper East Side tipped off police.
Authorities said the suspect attempted to assault a 21-year-old woman inside an apartment building around 4:35 a.m. on Sunday. Police believe the same man is connected to nine other sex abuse incidents.
The most recent incident took place Saturday night inside the subway station at 59th Street and Lexington Avenue. It would be the 10th incident of its kind since January.
Officers are ramping up the search for the suspect after another incident this weekend. The latest assault occurred Saturday afternoon inside the 59th Street and Lexington Avenue subway station.
Marcia Pena considers herself the latest victim in a long list of recent groping attacks on women in the city. It happened to her in Astoria, Queens, on a sidewalk on Steinway Street Sunday afternoon.
Video from a subway station at 77th and Lexington shows the man police suspect in a string of groping attacks dating back to May.