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Updated at 11:35 p.m. ET: Authorities are searching for a possible serial killer who has gunned down three Brooklyn business owners since the summer -- police believe the victims could have been targeted because they were Middle Eastern.
Detectives who specialize in hate crimes and FBI analysts who specialize in behavioral analysis have joined the case, authorities said.
Police Commissioner Ray Kelly said Monday that police are trying to identify a tall, balding man with a mustache who was seen on surveillance video carrying a black duffel bag near the scene of the latest shooting. NBC 4 New York has learned the same man was also seen on video near the second shooting in August.
Authorities say two other possible witnesses seen on video have been questioned and released.
The latest victim, 78-year-old Rahmatollah Vahidipour, a Jewish man from Iran, was killed Friday in his women's clothing boutique on Flatbush Avenue.
"The possibility of a bias motive here is something that can't be excluded," Kelly said.
After the latest killing, detectives discovered the same gun was used in the fatal shootings of two other shopkeepers when ballistics matched the .22-caliber gun shell casings on all three.
On July 6, Mohamed Gebeli, 65, an Egyptian immigrant and a Muslim, was found shot in the back of his shop, Valentino Fashion Inc. On Aug. 6, Isaac Kadare, 59, also Egyptian but Jewish, was shot in the head in his store, Amazing 99 Cent Deal.
There were other similarities, authorities said: The bodies were all partially obscured by clothing or, in one case, a box. The shops all lacked surveillance cameras, and the owners were alone in the store. The locations of the shops are each about four miles apart, with addresses that contain the number eight. Money was taken from everyone but Vahidipour, who had $171 in his pocket.
"We're trying to put it together. We're talking to the FBI; we're doing an all-out effort to solve these murders," Kelly said.
Kelly said it's reasonable to think the shooter had canvassed the area to find locations where no cameras existed.
"Here you have three stores where the proprietor is there by himself, no cameras in any of these," he said. "You'd have to speculate that some sort of reconnaissance was going on before the murders took place."
Kelly said they would like the tall man to come forward and identify himself. The commissioner said no one has been named a suspect and no arrests had been made.
The killings chilled local shopkeepers.
"Pretty nerve-wracking that a serial killer is on the loose in Brooklyn. You know it's the third one with the same gun," said Howard Prince, the manager of a business near the She She Boutique. Prince said police were stressing that no one should work alone.
"I mean that's not the part that concerns me," Prince said. "The part that concerns me is you take somebody's life that's 78 years old for no reason."
Kelly said city shop owners should be alert and aware of their surroundings and should call police or 911 at the sign of trouble.