I remember watching a film a couple of years ago that was made in '97 called "Paths to Paradise" - it was about the run up the '93 WTC bombing, and the botched attempt by police to apprehend the terrorists before the bombing.
Afterward the bombing, the police managed to apprehend all the bombers except one who managed to secure a helicopter ride out of America (the film stated on closing that he was later arrested overseas). One of the cops featured in the movie was referring to the impossibility to catch Islamic terrorists entering America, due to the shear volume of Muslim immigrants. The closing scene of the film showed the escaped terrorist flying past the WTC in the helicopter, with him stating "Next time, we will bring them both down." - it freaked me out how accurate the prediction proved!!!
And it wasn't the NYPD that botched the investigation, it was the FBI, one of the most hapless federal investigatory agencies, which has been adrift ever since the death of Jay Edgar Hoover.
If I recall correctly, they were the ones who allowed Mr. Yassin to flee to Iraq after some initial questioning in the wake of the '93 bombing.