UNPOSSIBLE! NYC is a police state, and it is illegal to carry a gun unless you have one of them fancy permits, which are harder to find than a virtuous woman on 5th Avenue!
This was a one-on-one assassination. This was not a crime of momentary passion, it was premeditated and carried out in almost cold blood. The flight and spray of gunshot against other unarmed pedestrians was probably because of realization that things had gone wrong, in an effort to commit suicide by cop, a not uncommon way to avoid arrest and indictment.