NYPD Officer Thomas Accomando was on his way home to New Rochelle when he saw a crime in progress in Fordham Heights.

"While at the stop sign, literally right in front of my car, this guy (was) punching another guy in the face and stomach," Accomando recalls. "I told him I'm a police officer, tell me what happened."

The 22-year-old victim, clutching his stomach, stammered out that he'd been mugged by a group of three guys who beat and robbed him.

As the suspects fled, the off-duty Accomando called for help and gave chase. Sgt. Vladimir Garcia and his partner helped corner the trio on Jerome Avenue.

They have been identified as Stephen Stith and brothers Antolin and William White. All three face robbery charges.

Police recovered the victim's cash, coat, sneakers and cellphone.