We were wondering what the NYPD helicopter was doing over Greenpoint late yesterday afternoon. It turns out that on Engert Avenue former narcotics cop Jerry Bowens, a witness in the investigation of corruption in the NYPD’s Brooklyn South, had just allegedly shot girlfriend Catherine Donofrio dead and wounded her female friend. Cops later responded to Bowens’ call from a motel room in New Jersey, but found it empty; they caught up with Bowens in Staten Island early this morning and took him in. Bowens had been nabbed in a narcotics squad investigation and was reportedly cooperating against a sergeant. The tabs have suitably lurid photos related to the case: the Post shows Bowens appearing to wink from the back of a squad car, and the Daily News shows Donofrio’s friend, Melissa Simmons, dazed and being escorted by an EMT who, behind her back, appears to gesture to a colleague that the second victim has suffered a head wound.