He described the man as wearing an overcoat and carrying a duffel bag.
Police say they are also looking for an older woman who may have witnessed the most recent killing. That occurred Friday when an Iranian shop keeper was shot to death inside his boutique in Brooklyn.
Authorities say two other possible witnesses have been questioned and released.
Rahmatollah Vahidipour was shot to death at the She She boutique. The video shows two people walking along Flatbush Avenue around 6 p.m. Friday and two others - a man and woman - seen running near the scene just 20 minutes before the 78-year-old victim was found dead.
Vahidipour's body was reportedly dragged to the back of the store and covered with merchandise.
"I hope that they find who it is and justice be served," one area resident said. "Because this was a good man."
The victim was the third Brooklyn businessman killed in his store since July, and police have now linked the same gun to all three murders. On July 6, clothing store owner Mohamed Gebeli was killed inside Valentino Fashion in Bay Ridge. On August 2, Isaac Kadare was found dead at his Amazing 99 Cents Deal shop in Bensonhurst.
None of the shops had video cameras. All had the number eight in the address. All of the victims were men of Middle Eastern descent and were over the age of 50.
"The possibility of a bias motive here is something that can't be excluded," Kelly said. "We're trying to put it together. We're talking to the FBI; we're doing an all-out effort to solve these murders."
Authorities are now offering a reward of up to $40,000 for information leading to an arrest and conviction in the three homicides.
Anyone with information about them may call the Crime Stoppers hotline in confidence at 1-800-577-TIPS.