Call it a crime of opportunity, against an all-to-common victim in Manhattan: a vulnerable female, walking home alone. "For no one to see or stop to help her. That's nothing to laugh at," said Lisa Blair.

Police say no one saw a thing, expect for the female victim, who helped police release a sketch of her attacker, described as a Hispanic male in his 30's. "In my opinion, it's getting dangerous," said a man walking in the Inwood Hill Park. Just steps from a stretch of bars and restaurants on Dyckman Avenue and Henry Hudson Parkway, detectives say a shirtless sex psycho followed a 28-year-old woman walking near the fields of Inwood Hill Park, pulled her into a secluded area, assaulted her then fled on a red mountain bike. "I would like to just hope it's a random, kind of a thing," said a neighbor.

The attack in Inwood happened around 8 p.m. Saturday. Hours later, at 2:30am, just a couple miles away in an unknown location in Washington Heights, police say another woman was sexually attacked. this time just steps away from her apartment This surveillance video of the suspected pervert shows him running from the building. Police say he held his 37-year-old victim at knifepoint, then hauled her up to the 8th floor where he attacked and robbed her. The suspect is also a Hispanic male in his 30s. This is the most recent in a week-long rash of sex attacks in Manhattan stretching from Inwood to the Financial District. "Three in a weekend, that's nothing to laugh at."

Women say the statistics prove it could happen to anyone. "My father told me at a very young age, there's absolutely no reason to be in a park after dark -- the end."

Police are asking for help in identifying the suspects. If you have any information, please CrimeStoppers at 800-577-TIPS. All calls will be left confidential.