A mysterious man toting a duffel bag has been identified as a key “person of interest” in the Brooklyn serial-killer case — after surveillance video showed him at one and possibly two of the three slay scenes, law-enforcement sources told The Post yesterday.

Cops said they are eager to talk to the mustached man — whom they dubbed “John Doe duffel bag” — about the killings of three Middle Eastern shop owners, each shot with the same .22-caliber gun over the last four months.

The unidentified man, who is middle-aged, white and balding, was most recently caught on surveillance video, duffel bag in hand, at around 6 p.m. Friday near the Flatbush store where owner Rahmatollah Vahidipour, 78, was found dead at 7:11 p.m., cops said.

Another video appears to show the same man near a Bensonhurst shop on Aug. 2 around the time its owner, Isaac Kadare, 59, was killed there, several sources said.

The duffel man has no known connection to the first murder — of shopkeeper Mohammed Gebeli, 65, in his Bay Ridge clothing store on July 6.

More On This...

“We want to identify the man known as John Doe duffel bag,” said NYPD spokesman Paul Browne.

Click here for more from The New York Post.